All Gens Tiering Nomenclature

The Pokémon Perfect Tiering Nomenclature is made up of 6 parts:

Tiering System	(Sub)Generation	Tier Set	Tier Level	Tier Stage	Tier Label
Pokemon Perfect	RBY	Standard	1	U	(Universal)

• The Tiering System usually refers to the Community to whom the tier belongs. This is usually ommitted when referring to a tier if the context is clear. Other communities use different Tiering Systems and as a consequence it might not be either possible or sensible to describe their tiers in the same format as we do here.
  
• Sub(Generation) refers to the specific set of game mechanics used. A Generation's mechanics usually refers to the game mechanics of the latest released main series game (not Stadium or XD), while the specific game or SubGeneration is always named in the case of the Stadium or XD classes of Tier Sets.
• The Tier Set refers to the chosen restrictions on a battle mode, that defines the overall rules, which are inherited through tier levels. When referring to a tier, the Tier Set is usually omitted when it is Standard. The Standard tier set follows main series cartridge mechanics and allows standard legal sets of that generation without additional limitations imposed that are not for balance or diversity-related reasons, and is played in Singles. Other examples of Tier Sets include Little Cup (LC), Doubles, No Wrap, Hackmons and others.
  
• The Tier Level numeral represents the nth tier level in a tier set. Each new lower tier level forms from a broad cut-off of what is viable in the existing higher Tier Level e.g. RBY 1, or RBY 2 (ban transitivity from RBY 1), RBY 3 (ban transitivity from RBY 2).
  
• The Tier Stage Letter differentiates one Stage from another in a Tier Level - i.e. higher stages have fewer bans and therefore are less developed tiers than their lower counterparts e.g. RBY 1P compared to RBY 1U.
  • A is reserved for the alpha stage of tiering, or Anything Goes in tier level 1.
    
  • B,C, D... then follow on with more and more bans.
    
  • P is reserved for traditional tiers such as RBY Ubers and BL where no higher Pokémon are banned (the primal stage/tier of the tier level).
    
  • Q, R, S... are tiers in between the traditional broken and main tiers where less broken Pokémon are banned.
    
  • U is reserved for the main tier, or 'Used tier' of the tier level.
    
  • V, W, X... explore alternate tiers where Pokémon could be banned.
    
  • The initial order of existence is A, then B...If a balanced tier is finalised in a tier without any additional bans, A will be renamed to U. If there are Pokémon bans, a P tier will be formed. If there are more than one set of bans, the other letters will be used.
• The Tier Labels are displayed within brackets. Tier Stages that have a player base are labelled as Tiers. These names are aimed at increasing clarity to those familiar with a separate Tier System.
  • Main tiers follow this labelling system within every tier set:
    • 1U = OverUsed = OU
    • 2U = UnderUsed = UU
    • 3U = UnderUnderUsed = UUU
  • The number of Us in the main tier label corresponds to the tier's level.
    
  • The tier label for the first stage of the first tier level is Anything Goes (the chaos tier in which all other tiers in the set inherit bans from).
  • Other broken tiers are either referred to as Ubers/BL, or based on the Pokémon they allow, such as RBY Mewbers.
  • The tiers for the first tier stages in a level otherwise have alpha, beta, gamma... appended to the main tier label to convey the progression of the main tier as it is balanced stage by stage.

Example Tier List:

XYZ 1A (Anything Goes) <-- Tier level 1 alpha stage (no bans)
XYZ 1P (Ubers) <-- Tier level 1 primal stage (no Pokémon bans)
XYZ 1U (OverUsed) <-- Tier Level 1 main tier (balanced stage)
XYZ 2P (BL) <-- Tier Level 2 primal stage (no non-inherited Pokémon bans)
XYZ 2U (UnderUsed) <-- Tier level 2 main tier (balanced stage)
XYZ 3P (BL2) <-- Tier level 3 primal stage (no non-inherited Pokémon ban)
XYZ 3U (UnderUU) <-- Tier level 3 main tier (balanced stage)
XYZ 4A (Under3U Alpha) <-- Tier level 4 first stage
XYZ 4B (Under3U Beta) <-- Tier level 4 second stage

For more detailed description on some of the concepts, see Tiers Jargon.