Harry Potter/Harry Potter and The Half-Blood Prince

"Apparently I underestimated you, Potter. Who would have thought you knew such Dark Magic?"

—Severus Snape

In the sixth Harry Potter book, published in 2005, the Ministry has finally accepted that Voldemort is back, but that's not really making the situation any better. With everyone terrified, obviously unjustifiable arrests, and misinformation still being printed, just in the other way, and events play out to show that the Ministry can't really stop Voldemort in its current form.

But while those events linger over the plot, the action stays fully grounded at Hogwarts. Harry learns more about Voldemort's Backstory, becomes increasingly suspicious of Snape's loyalty and discovers an old potions textbook annotated with powerful spells and useful notes from its previous owner who identifies himself only as "The Half Blood Prince". Draco Malfoy joins the Death Eaters only to discover that Evil Is Not a Toy; and wacky romantic hijinks ensue for everyone.

As Word of God has noted, Half-Blood Prince is where the serialization of Harry Potter hit its max. Where all five of the previous novels ended the main plot, Half-Blood Prince's ending builds up to an emotional release but simply prepares the reader for Deathly Hallows to start up at a much faster pace.

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Tropes exclusive to this book or at least especially prominent:

• Accidental Kiss: Harry and Ginny. Type 1.
• Acquitted Too Late: Morfin Gaunt, who was framed by Voldemort for the murders of Tom Riddle Sr. and his parents. Dumbledore found evidence Voldemort was the real culprit but Morfin didn't live long enough to see the verdict being overturned.
• Actor Allusion: Horace Slughorn accidentally refers to Ron as Rupert.
• All for Nothing: Considering what it ultimately costs them, and that the locket was a fake, Harry and Dumbledore's jaunt into the cave proves quite fruitless.
• Ambition Is Evil: Finally averted in the person of Horace Slughorn, which is nice given that he is a member of Slytherin, the Former Trope Namer. He has a tendency for favoritism, singling out people he hopes will benefit him in the future due to their talent or family connections, but even this is equal-opportunity and he doesn't hold (much) prejudice against other houses or non-purebloods. He is also genial, more likable than all prior Slytherins (Draco in Leather Pants notwithstanding), is ashamed of accidentally helping Tom Riddle's Start of Darkness, and isn't, you know, evil.
  • It's also mentioned that the people he singles out really do have knacks for going far in life (which is why he makes favorites of Hermione and Ginny, even though they aren't from prominent families). So it's really a win-win for both sides, with him providing opportunities to students that they might not get otherwise and them sending him various gifts in exchange. If you think about it, its no worse then a College Professor giving a student they think has potential pointers and tips.
• Ascended Extra: Ginny, who goes from minor character to a rather vital person in Harry's life. The film at least tries to temper this by giving her an even bigger role than in the novel.
• Asshole Victim: Played with, Tom Riddle Sr. had a reputation as a Rich Jerk in his town but Merope effectively kidnapping and date-raping him with a Love Potion still comes off as morally wrong to many.
  • Also with Morfin Gaunt, Muggle-hater who was framed with the murders of Tom Riddle Sr. and his parents, all of whom were asshole victims on their own right.
• Batman Gambit: Dumbledore is trying to arrange his own murder, for the sake of keeping the Elder Wand from Voldemort. Draco shoots it all to hell somewhat when he Disarms Dumbledore before the other Death Eaters arrive on the Astronomy Tower.
  • Hey, it still worked. Just not in the way it was intended to.
• Beauty to Beast: Bill. Also Voldemort's back story, due to his own efforts.
• Beneath Suspicion: Nobody believes Harry as he argues that Draco is a Death Eater plotting against them, since Draco is mostly a joke to them by this point.
• Bilingual Bonus: In Latin, fēlīx, fēlīcis means "lucky". ^[1]
• Blood Magic: As revealed by a memory given by Slughorn, one of the steps in creating a Horcrux is to commit murder. Also Dumbeldore has to cut his own hand to enter a cave Voldemort has protected with Dark Magic, which has the added fringe benefit of weakening any intruder, leaving them vulnerable to other forms of protection.
• Breather Episode: Between the Umbridge-a-riffic fifth book and the Kill'Em All Seventh, most of this book is a pretty easy-going tale with a lot of exposition and teen angst (not to mention many jokes). That is, until the last few chapters, where it turns into a Wham! Episode...
• Call Back: And lots of them, some easy to miss. Some of them are harsh, such as Harry going to Diagon Alley with Hagrid and meeting Draco in Madam Malkin's... only Diagon Alley is no longer the wonderful wizard bazaar of the first book, but under war conditions. Some of them are more cheery, like the callback to the scene in the last book where Harry was embarrassed to be sitting with the uncool Neville and Luna when he sees his crush Cho; this time round Harry's new groupie Romilda Vane invites him to come sit with her rather than sit with the uncool Neville and Luna, only for Harry to coldly tell her that they're his friends.
  • This Crowning Moment of Heartwarming:

Hermione: "You said to us once before that there was time to turn back if we wanted to. We've had time, haven't we?"

• Calling Your Attacks: Mostly played straight, as in the previous books, but averted when Snape begins teaching non-verbal spells in Defense Against the Dark Arts.
• Cassandra Truth: Harry, dear, when you accuse someone of something it helps to have evidence backing you up.
• Cheaters Never Prosper: Two examples. One inversion and one subversion. The first is when Hermione uses a Confoundus charm on Cormac to make him miss his last block, ensuring Ron gets the position of Gryffyndor Quiddich Team keeper. The second is when Harry puts Felix Felicis in Ron's drink, which is forbidden; however, it turns out he didn't actually put it in. Ron only thought it did, and it gave him the confidence boost he needed to win .
• Chekhov's Gun: The series has its own page.
• City Mouse: Fleur Delacour. She doesn't appear to realize how much this aggravates her future in-laws (but there's clearly animosity on both sides).
• Clingy Jealous Girl: Lavender.
• Compliment Backfire: Ron praises Luna for her performance as a commentator in a Quidditch match. Ron is sincere, but Luna isn't so sure since everybody else tells her she did poorly.
• Continuity Lock Out: Formally takes effect, Rowling dispenses of the--rather tedious--recap chapter that all of the other volumes starts with.
• Convenient Terminal Illness: It turns out that Dumbledore had been dying for the entire book before he asked Snape to kill him.
• Cool Teacher: For all his favoritism, Slughorn does deliver an impressive first Potions lesson.
• Creepy Child: Tom Riddle
• Cuckoolander Commentator: Luna during the last Quidditch match.
• Curb Stomp Battle: Harry vs. Snape is quite possibly the single most one-sided duel in the book besides Snape's earlier bouts with Lockheart.
• Dangerous Forbidden Technique: The creation of a horcrux is so forbidden that there's virtually no information on how to do it besides "kill somebody".
• Dark Is Not Evil / Dark Is Evil: The new Defense Against the Dark Arts teacher Severus Snape imparts his personality onto the classroom and adorns the walls with plenty of pictures showing the various horrid things that happen to anyone who runs afoul of the Dark Arts.
• Deader Than Dead: Inferi. They're like zombies and thus have to be burned; other forms of magic such as Sectumsempra won't work because they have no blood and feel no pain.
• Dead Man Writing: The mysterious R.A.B.
• Death by Childbirth: Merope Riddle.
• Designated Love Interest: Ginny. Part of the hate for the pairing of Harry and Ginny is because of Die for Our Ship, while the other part is rooted specifically to this. After her questionably rushed hook-up with Harry, most of the development of the pairing took place off screen. In fact, there's a time skip following their hookup where Harry describes it at as some of the happiest moments in his life, but the readers never actually get to see it.
• Despair Speech: Slughorn gives one of this when he agrees to give Harry his memory about the time he told Tom Riddle about the Horcruxes.
• Disappointed in You: When Harry disappoints Dumbledore by not making much of an effort to get a memory from Slughorn, he would have preferred him to yell; "this cold disappointment was worse than anything."
• Due to the Dead: Many students attend Dumbledore's funeral.
• Enfante Terrible: Tom "I can do bad things to people who annoy me. I can make them hurt if I want to" Riddle.
• Et Tu, Brute?: Snape's murder of Dumbledore plays with it, although it is ultimately subverted in the next book, where it is revealed that this was in fact done because Dumbledore was dying anyway due to the curse from the ring horcrux that withered his arm, and in fact Dumbledore actually came up with the idea for Snape to do that.
• Even Evil Has Standards: Even most dark spellbooks are reluctant to elaborate on the nature or creation of Horcruxes.
• Everyone Can See It: Ron and Hermione.
• Evil Is Cool: Used In-Universe with Snape as the Dark Arts teacher. Harry, upon hearing him talk about the Dark Arts thinks It was surely one thing to respect the Dark Arts as a dangerous enemy, another to speak of them, as Snape was doing, with a loving caress in his voice?
• Evil Is Not a Toy: Draco is proud to be working for Voldemort... to begin with.
• Fake Memories: Slughorn has covered up his own memories of giving the young Voldemort information about the Horcruxes.
• Foe Yay: Thank God Harry's obvious obsession with Draco was eaten by the giant chest monster, who decided to save the appearances just in time.
• Foreshadowing: In the film at least: Just before Harry arrives to retrieve the locket horcrux, Dumbledore and Snape are overheard getting into an arguement regarding a task Dumbledore entrusted Snape with. The next book reveals that the "task" was in fact Snape's "betrayal" and murder of Dumbledore, although its more complex as being more comparable to Assisted Suicide as Dumbledore was dying anyways from destroying Marvolo's ring and getting a curse on it.
• Free Sample Plot Coupon: After Dumbledore tells Harry about the importance of destroying Horcruxes, the latter is concerned about the potential difficulty of finding said artifacts in the first place, but then the headmaster tells him that he had already destroyed Marvolo's Ring, and that Harry himself had destroyed Riddle's Diary in Chamber of Secrets, so there are only four more Horcruxes to worry about.
• Friend Versus Lover: Hermione vs. Lavender and Parvati vs Ron.
• Geas: The Unbreakable Vow.
• Getting Crap Past the Radar: When Ron and Hermione try and fix the former's misspelled essay due to a worn out auto-correct quill, one of the things Hermione notes is "Augury doesn't begin with O-R-G' either.'
• A Glass in the Hand: Dean Thomas after seeing Harry and Ginny kiss. Romilda Vane seems to be even angrier, as she is described as looking like she's about to throw something.
• Gotta Kill Them All: The quest to find and destroy all of the Horcruxes.
• Heroes Want Redheads: Harry and Ginny.
• Imperial Stormtrooper Marksmanship Academy: Justified via Felix Felicis.
• I Need to Go Iron My Dog: Dumbledore uses this method to leave Harry alone with Professor Slughorn so as to persuade him to return to Hogwarts -- specifically, by asking to use the loo. The fact he returns afterwards with a magazine he wants to keep "for the knitting patterns" just highlights his eccentricity and hilarious kookiness. It was still a nice bit of obfuscation.
• Insecure Love Interest: This is Lupin's reason for not getting together with Tonks. He comes round in the end.
• Inspector Javert: Harry to Draco.
• Insult Backfire: "Dumbledore's man through and through, aren't you?" "Yeah, thanks for clearing that, Minister."
• Is That What They're Calling It Now?: Right before Christmas vacation, Ron and Lavender are described as "saying a thoroughly nonverbal good-bye".
• It's Not You, It's My Enemies: Harry has to tell Ginny this. She knows exactly what he's trying to do and ignores it.
• Just Between You and Me: Dumbledore encourages Draco to go on about his plans in order to buy time. Since Draco is reluctant to kill him, he complies.
• The Ketchup Test
• Kick the Dog: Greyback attacked the five-year-old son of Ms. Montgomery when she refused to cooperate with the Death Eaters. The boy later died from his injuries.
• Kill It with Fire: Dumbledore specifically states that fire is the most effective against Inferi. The Ring of Fire he uses in the cave is even in the British cover pictured above.
• Knowledge Broker: Slughorn.
• Last-Minute Hookup: Not only do Harry and Ginny become a couple close to the end after Harry spends a good portion of the book crushing on her, but they actually manage to break up before the end of the book!
  • Doubly so because the novel glosses over the few weeks Harry grows closer to Ginny, in the span of a chapter going from crush to couple. The film rectifies this a bit by expanding Ginny's screen time and giving her more scenes alone with Harry.
• Lighter and Softer compared to the politically-charged previous novel and the Kill'Em All final novel this book, while dark, focuses on the teen romances and serves as a Breather Episode
• Losing the Team Spirit: Dumbledore's death has this effect on the entire school.
• Love Epiphany: Harry's chest monster.
• Love Potion: Part of the merchandise at Fred & George's joke shop. One of Harry's fangirls attempts to trick him into eating a box of chocolates spiked with them. Hilarity Ensues when Ron eats them instead.
  • In addition, this seems to be the entire reason that Lord Voldemort exists in the first place, as his mother had used a Love Potion on a snobbish Muggle - Tom Riddle Senior.
• Love Dodecahedron
• Lowered Recruiting Standards: Harry & Ron, among others, get into NEWT Potions because Slughorn has lower standards than Snape.
• MacGuffin: Voldemort's Horcruxes
• Magic Feather: Harry pretends to give Ron a luck potion to give him confidence. A slight subversion in that the potion would have actually worked if added for real, but its use in contests is of course banned.
• May-December Romance: Lupin and Tonks. He's in his late thirties. She's in her early twenties.
• Meaningful Echo: "Don't worry, Harry, you are with me," becomes "I am not worried, Harry. I am with you." Former Trope Namer.
• Meaningful Funeral
• Mentor Occupational Hazard: Dumbledore.
• Meta Twist:
  • Slughorn is set up as the new-DADA-teacher of the book. Harry is as surprised as the reader to learn he's actually replacing Snape, who's moved positions after wanting the job for years.
  • Two previous Red Herring characters are behind the main plot, and this time Harry is on to them from the beginning. So is Dumbledore, but he's keeping quiet about it in case Voldemort catches on through Legilimency.
• Mind Rape: Dumbledore goes through this while drinking the potion guarding the locket Horcrux.
• My Greatest Failure: Slughorn revealing information about Horcruxes to a young Tom Riddle.
  • We hear Dumbledore going through his during his mind rape.
  • Also Snape's feelings about giving Voldemort the prophecy and dooming James and Lily, though Harry believes this to be a lie at the time.
• My Sister Is Off-Limits: Harry struggles with this, but when he does decide to date Ginny, it's strongly implied that if there was anyone that Ron was all right with Ginny dating, it was Harry.
• Mythology Gag: It can not be mere coincidence that Slughorn once misstates Ron's name as "Rupert".
• No Matter How Much I Beg: Harry, Dumbledore and the Horcrux-containing potion. Harry keeps his word, but only barely.
• Non-Indicative Name: In-universe example. Love potions can't actually create love, only infatuation.
• No Ontological Inertia: Dumbledore's body-bind spell. There are hints throughout the books that this is a common and expected phenomenon -- magic dies along with the wizard that performed it. In a brilliant bit of Adaptation Expansion, the movie uses this to discuss Slughorn's relationship with Lily Potter.

Slughorn: I once had a fish... Francis. He was very dear to me. One afternoon, I came downstairs and... it vanished. Poof.
Harry: Poof.
Slughorn: It was a student who gave me Francis. One day I came down to my office, and there was a bowl with only a few inches of clear water in it. And there was a flower petal floating on the water. Before my eyes it started to sink, and just before it hit the bottom, it transformed into a wee fish. It was a beautiful piece of magic, wondrous to behold. The flower petal was from a lily. The day Francis disappeared was the day your mother... (starts crying)

• Not a Date: Harry and Luna at Slughorn's party. He makes it clear that they're going as friends, which she is perfectly happy with - Peeves, of course, overhears them and zooms off cackling about how "Potter loves Loony."
• Not-So-Harmless Villain: Draco Malfoy. In the previous books, he was a bully, but not even a pawn when it came to Harry vs Voldemort. But in this one, Harry will get serious trouble because of him.
• Not Using the Z Word: Inferi are basically magical zombies with a different name. (The original voodoo / vaudou kind, not the modern post-George Romero kind.)
• Obviously Evil: Tom Riddle, as a child in the orphanage, to the point where even though nobody can prove anything he scares everyone, even those who run the orphanage. By the time he gets to Hogwarts he becomes very good at hiding this, enabling him to fool everyone except Dumbledore, who met him before he adopted the act.
• Only Smart People May Pass: The protection around the Horcrux ensures that it's impossible for anyone (including Voldemort himself) to get at it without hideously torturing them.
• Operation: Jealousy: Implied, but not stated outright, to be the reason Ron dated Lavender Brown. Hermione later does a much more obvious version when she takes Cormac McLaggen to the Christmas party. In the novel, she informs Harry that she considered Zacharias Smith in trying to figure out who would upset Ron more.
• Part-Time Hero: Harry frequently neglects preparation for his battle with Voldemort in favor of sports and dating. Snape calls him on this during their battle at the end of the book.
• Perpetual Poverty: Finally averted by the Weasley Twins, who take Harry's Triwizard winnings as seed money and build a very lucrative business in Diagon Alley.
• Please Dump Me: Ron takes the coward's way out and just pretends to be asleep every time Lavender visits him in hospital, to Harry's exasperation.
• Properly Paranoid: Harry (finally) turns out to be right about Malfoy being a Death Eater and planning something.
• Psychic-Assisted Suicide: a rabbit at Tom Riddle's orphanage is made to hang itself.
• Psychosomatic Superpower Outage: Tonks loses control of her metamorphmagus powers in her depression over both Sirius' death and her feelings for Lupin. We later learn that this also happened to Merope, when she was under the thumbs of her brother and father.
• Rape Is Love / Rape Is Okay When Its Female On Male: The love potions. They're basically the magic world equivalent of date rape drugs. Yet, using them is portrayed as sweet and innocent because it's the girls using them on the boys. Just imagine the uproar of the Moral Guardians if any of the boys were shown using them on the girls.
  • Deconstructed with Merope's rape of Voldemort's father, which is portrayed as a very bad thing not just in and of itself but because it meant Tom Riddle wasn't conceived out of love, making him evil. The reason it's played for laughs with Ron is that Harry kept anything untoward from happening. And it's possible the Double Standard exists in the HP universe, and Merope was put in deliberately, to highlight it.
• Rasputinian Death: Dumbledore. Let's see ... . He gets an arm nearly burned off from a curse -- a curse that proceeds to slowly drain his life force away. Later he has to slice open his arm for a blood tribute. He drinks all that poison to retrieve the fake Horcrux. Then he gets a Killing Curse right in his chest and tumbles off the balcony of the tallest tower in Hogwarts.
• "The Reason You Suck" Speech: Played with, as it's not delivered by the Big Bad, but Snape does give Harry a rather good one when they are dueling at the end - and, in hindsight, it's very easy to interpret as Snape getting one last chance to say to Harry, "No, seriously, get better at the things I was trying to teach you or you are going to frigging die."
  • Harry also delivers one to Rufus Scrimgeour.
• Rescued from the Scrappy Heap: In-universe example. Fleur's insistence on marrying Bill forces Molly to admit that her future daughter-in-law is a far, far better person than she had given her credit for.
• Red Herring: Both Inverted and Hand Waved: the book starts out with Snape giving Bellatrix (and by extension the readers) a detailed accounting of himself during the previous books to make it plausible he could still be working for Voldemort despite the previous buildup of him as a bad-mannered but otherwise trustworthy good guy.
• Romantic False Lead: Dean Thomas.
• The Reveal: Snape was the Death Eater who told Voldemort about the prophecy, bumping Lily and James to the top of his list. Harry, naturally, learns this minutes before going after a Horcrux with Dumbledore. It takes everything he has not to start tearing the office apart like at the end of the last book.
• Self-Made Orphan: Although it was hinted at in Book 4, this one confirms that Voldemort killed his father, Tom Riddle Sr.
• Shaggy Dog Story: Did you hear the one about how the Horcrux Harry and Dumbledore nearly killed themselves trying to retrieve from the cave turned out to be a fake, planted by someone else to buy the resistance some time for when Voldemort came back to get it?
• Shown Their Work: When it is revealed that the only side effect Fenrir's bite will have on Bill is a preference for very rare steaks, Fleur declares that it is lucky that he is marrying her because "ze British overcook their meat." There is a French term "bleu" which is decidedly rarer than the British/American "rare". Essentially, it is just seared. The surface is cooked, but the inside is not really cooked at all.
• Ship Sinking: Though not officially torpedoed until Book 7, this book effectively sank the ship of Harry/Luna. However, it does still give the readers some...
• Ship Tease: Harry and Luna get some moments, such as him telling her she's cool, refuting his thoughts about her from Book 5 and when he takes her to Slughorn's Christmas Ball. After he asks her to go with him, Peeves also becomes a Ship Tease and starts singing, "Potty loves Loony!"
• Shotgun Wedding: Merope was hoping to have one of these with Tom Riddle Sr, or at least have him stay with her due to her pregnancy.
• Sickeningly Sweethearts: Bill and Fleur (as far as Ron and Ginny are concerned), Ron and Lavender (mainly the latter).
• Smooch of Victory: Harry kisses Ginny after she wins Gryffindor the Quidditch cup. (Also an Accidental Kiss). In the movie it happens between Ron and Lavender.
• Some of My Best Friends Are X: Variant - the one bringing this up isn't the one being accused of prejudice. When Slughorn talks about how surprised he was that Muggleborn Lily was so good at potions, Harry mentions that one of his best friends is Muggle-born and she's the best in their year.
  • Slughorn plays it dead straight immediately after, denying any insuations that he's prejudiced by rapidly pointing out that he's got several favourite Muggleborn students.
• Soul Jar: The Horcruxes.
• Spinning Out of Here: Apparition is triggered by spinning in place.
• Supernatural Sensitivity: in the cave scene, Dumbledore is shown to determine where the secret entrance is and the spells used on it without the use of any detection spells.
• Stalker with a Crush: Romilda Vane.
• Switching POV: To show us Snape's vow.
• Tampering with Food and Drink: Ron accidentally eats love-potion-spiked chocolates meant for Harry. Harry gets Slughorn to give him an antidote before things get out of control...and then he drinks poisoned wine meant for Dumbledore.
• Thanatos Gambit: Albus Dumbledore, though we don't learn it until the next book.
  • Also, apparently, RAB.
• Tonight Someone Dies: Dumbledore. Rowling had announced before the book's release that a major character was going to be killed off.
• Ugly Guy, Hot Wife: After Bill is mauled by Fenrir Greyback the Werewolf, Fleur still loves him. This is what finally convinces Ginny and Molly Weasley to accept her.
  • Inverted with Merope Gaunt and Tom Riddle.
  • Played straight with Lupin & Tonks. Though we're sure some fangirls will insist otherwise. After all, Lupin is actually handsome, its just his age and his lycanthrophy puts the odds against him.
  • Also played straight with Mr and Mrs Delacour.
• The Unchosen One: Dumbledore makes a point of making Harry realize that, regardless of the prophecy, what Harry does is his own decision and no one else's.

Harry Potter: But, sir, it all comes to the same thing, doesn't it? I've got to try and kill him, or --
Albus Dumbledore: Got to? Of course you've got to! But not because of the prophecy! Because you, yourself, will never rest until you've tried! We both know it! Imagine, please, just for a moment, that you had never heard the prophecy! How would you feel about Voldemort now? Think!
Harry: I'd want him finished. And I'd want to do it.

• Unusual Euphemism: "Chest monster" is certainly an original term, though anyone who's been an adolescent male probably has no trouble sympathizing.
• Wham! Episode: Dumbledore's death.
• What Do You Mean It's Not Heinous?: Ron is horrified to learn that Hermione kissed Viktor Krum two years ago. And also that his little sister is kissing, period (and in empty parts of the school, no less).
• What Kind of Lame Power Is Heart, Anyway?: "So, when the Prophecy says, that I'll have 'Powers the Dark Lord knows not' it just means Love?" asked Harry, feeling a little let down. "Yes, just love" said Dumbledore.
• Will: Sirius Black made one naming Harry Potter as his sole heir.
• The Worf Effect: Harry Potter vs. Severus Snape. Snape takes the moment to say "Man you suck" as he flees. This was an extremely important fight for the books, as this makes it eminently clear that being the "chosen one" isn't going to mean crap if Harry still pretty much sucks as a wizard.
  • Though, to be fair, getting your ass kicked by Snape doesn't necessarily mean "you suck as a wizard" so much as it means "you're not one of the two-or-three most powerful wizards on Earth."
• Xanatos Gambit: Voldemort's plan (ordering Draco to kill Dumbledore) is a Xanatos Gambit. The plan is to give Draco an impossible, likely-suicide mission in order to punish Draco's father, Lucius, for his failures. But, hey, if Draco succeeds, all the better.
• Writing Lines: Seamus accidentally knocks Flitwick off his desk with a spell, and has to write "I am a wizard, not a baboon brandishing a stick".

1. ↑ Those are the nominative and genitive forms of the adjective; essentially, they're two different ways of saying the same word whose use depends on the grammatical role played by the noun it modifies. Notably, Latin nouns and adjectives are often displayed this way in high-school textbooks.