An archetype is a group of cards that respect the following rules:
- All members of that group of cards must contain a common term (the name of the archetype) appearing in their members' Japanese card names. Alternately, a card must contain an archetype condition in its card text that specifically states that the card belongs to a certain archetype (e.g. "Number 39: Beyond the Hope"). In the TCG, archetype conditions are sometimes added due to inconsistency when cards were translated from Japanese (e.g. "Chimera the Flying Mythical Beast" and "Axe of Despair"). Cards with the same words in their non-Japanese names are not necessarily part of the same archetype (e.g. "Frog the Jam" is not a "Frog" card).
- Superscript text is not considered by itself for archetype membership (e.g. "Neo-Spacian" monsters are not considered "Neos monsters, despite containing 「ネオス」 in their superscript). However, for archetype names that contain superscript text in their Japanese name, a card must also exactly match the superscript text and format to be a part of that archetype (e.g. "NEX" is not a "Neo-Spacian" card because 「ネオスペーシアン」 (Neo-Spacian) is not superscripted only above 「Ｎ」).
- There must be at least one support or anti-support card relating to the archetype; that is, a card that mentions "archetype monster", "archetype card", "archetype Spell/Trap card", etc. (prior to the Simplified Effect Text, "contains archetype in its card name") in its card text. Note that these cards must support the archetype, not only one member of the archetype.
Although membership in an archetype is dictated by the Japanese names of the cards, there are cases where the membership of a card in an archetype is unintentional. For example, "Thought Ruler Archfiend" is considered to be part of the manga-exclusive "Sphere" archetype, as its Japanese name ("Mental Sphere Demon") contains the "スフィア", the text for "Sphere", despite this card bearing no relation to the other members of the archetype.
The concept of archetypes is often used in the manga and anime series to define a character's personality, look, state of mind or style of play. Most major players did not use archetypes early on due to a lack of archetypes, but as the game developed, Kaiba and Yugi's Decks grew around an archetype, and Decks based on archetypes such as Mai Valentine's and Maximillion Pegasus's Deck appeared. Starting with the Yu-Gi-Oh! GX series, virtually all main characters and most minor characters utilized Decks based around archetypes.
Groups of cards with similar names and/or artworks that are not supported or anti-supported explicitly by card effects are called a series.