[[quoteright:330:http://static.tvtropes.org/pmwiki/pub/images/mini_dress_sister_tropes_5424.jpg]]
[[caption-width-right:330:MiniDressOfPower[[note]]from ''Manga/WeddingPeach''[[/note]] and SexySantaDress[[note]]from ''Anime/NeonGenesisEvangelion''[[/note]] are both skimpy dresses for {{Fanservice}}, but otherwise different purposes.]]

What happens when TheGloriousWarOfSisterlyRivalry switches genders? CainAndAbel. What's the [[CanonicalListOfSubtleTropeDistinctions difference]] between TheScrappy and a CreatorsPet? Authors love their Pet. Is this introductory paragraph trying to explain by example a XanatosGambit or a BatmanGambit?

When defining a trope, it often helps to establish its similarities, differences and relationship to other tropes; a common convention on this site is to refer to some tropes as Sister Tropes.

When two or more tropes have some overlap in their descriptions, "parentage", or use, but not enough for one to be a SubTrope or SuperTrope of the other, these are called {{Sister Trope}}s. That is, both have a similar form or function, either by category ([[CharactersAsDevice character]], [[{{Plots}} plot]]) or by effect ([[CharacterizationTropes characterization]]) rendering them both similar but distinct enough to be considered equals. [[PoliticalCorrectnessGoneMad Not that there's anything wrong with]] subtropes!

These are the four Trope Sisters, each more lovely than the last:
* '''Function:''' When two or more tropes serve the same function, but are notably different in execution.
** ''ExpressiveMask -- ExpressiveHair''
** ''StairwayToHeaven -- {{Hellevator}}''
* '''Form:''' When two or more tropes are similar in style but themselves unique, usually used for different purposes.
** ''ItsALongStory -- ToMakeALongStoryShort''
** ''ComplimentBackfire -- InsultBackfire''
* '''Same Parent:''' Subtropes of the same SuperTrope are frequently referred to this way.
** In AntiVillain: ''NobleDemon -- DarkMessiah''
** In PoorCommunicationKills: ''CanNotSpitItOut -- YoureJustJealous''
* '''Conjoined Use:''' They are different, perhaps a character and an attack, plot, or relationship, but see frequent (though not necessarily exclusive) use together.
** ''DoppelgangerSpin -- DoppelgangerAttack''
** ''ShapeShifterShowdown -- ShapeShifterSwanSong''

Sometimes when two distinct tropes serve almost exactly the same function or have [[CanonicalListOfSubtleTropeDistinctions very subtle differences]] in description, it can reach the point that they are used almost interchangeably. Bad {{Flanderization}}! ''Bad!'' The CanonicalListOfSubtleTropeDistinctions is your friend.
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!!Examples:
* It is possible to juggle a [[VillainBall Villain]], [[IdiotBall Idiot]] and ConflictBall all at once. IdiotBall doesn't necessarily make direct conflict, and ConflictBall doesn't necessarily make idiocy. Thus they are related, but not really covered by the other. VillainBall carrying may involve stupidly PyrrhicVillainy and cause conflict aplenty, but it doesn't have to.
* BigNo and ChewingTheScenery (or LargeHam) can often overlap, but not always.
* ImpracticallyFancyOutfit is a cause of the ErmineCapeEffect, but the latter trope is also responsible for the continued application of the former.
* RoyalsWhoActuallyDoSomething and LadyOfWar occasionally overlap.
* LethalChef and ItTastesLikeFeet are sister tropes.
* OneJudgeToRuleThemAll and GoldenSnitch are sister tropes.
* So are GargleBlaster and HideousHangoverCure.
* CastOfSnowflakes is what happens when those LoadsAndLoadsOfCharacters are given characterization.
* NiceJobBreakingItHerod, your {{Genocide Backfire}}d on us completely.
* HumanShield and BulletproofHumanShield both deal with bystanders being used to protect a target. The former discusses the psychological coverage, while the latter deals with physical protection.
* EvilTwin, EvilCounterpart, EvilKnockoff, and CriminalDoppelganger are all about evil duplicates of one person, but the evil persona in the individual tropes are an identical twin, a persona from an AlternateUniverse, an intentionally created duplicate, and an IdenticalStranger, respectively.
* DescendingCeiling and TheWallsAreClosingIn are both [[DeathTrap Death Traps]] that threaten to squash/crush characters trapped in them, but have different parts of the room move to achieve this.
* TheAce and ParodySue are closely related concepts with different intentions and execution. Both are (usually) played for comedy, but while the former is an idealized character who's over-the-top nature is played for laughs, the latter is a TakeThat against a fandom in general.
* InnocentFanserviceGirl and ShamelessFanserviceGirl. Both are girls who have no nudity taboo. But one is aware of the existence of nudity taboos, and the other isn't.
* BadassNormal and NonPoweredCostumedHero often overlap in certain contexts (most importantly probably the person of Franchise/{{Batman}}), even though the only thing they conceptually have in common is having no superpowers.
* XanatosGambit and BatmanGambit are both schemes to achieve benefit but they are executed differently. The BatmanGambit is based on FlawExploitation and/or what a given mark is most likely to do. Thus, it will fail if the mark doesn't behave as predicted. The XanatosGambit is based on MortonsFork: it can succeed no matter which prong the mark is impaled on. The benefits may be completely unrelated or they may be different paths to the same goal as long as every reasonable outcome benefits the planner in some what.
* UnnecessarilyLargeVessel regularly goes hand-in-hand with StarshipLuxurious. The main distinction is that StarshipLuxurious refers to the spaces inside the ship being much larger and fancier than is strictly necessary, while UnnecessarilyLargeVessel refers to the ship itself being bigger than it needs to be.
* {{Boarding Pod}}s and {{Drop Pod}}s are both for getting troops from a ship to a target in a [[DynamicEntry surprising fashion]]. The difference is the target: drop pods are launched onto a planet surface as a futuristic version of ItsRainingMen, while boarding pods are fired at other ships or at stations to deploy a BoardingParty.
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