Series
 | The name of this article is unofficial, or it uses unofficial terminology. It may change at any time as official terms are announced. |
Series (シリーズ Shirīzu) is an unofficial term used by the Yu-Gi-Oh! TCG community to refer to groups of cards with similar name, artwork, and/or effect design, but do not have a single shared name substring that is supported by a card effect that are present in archetypes. This term does not exist in the official rules of any Yu-Gi-Oh card or video game.
An example of a series is Digital Bug; there are cards with the "Digital Bug" name substring (e.g. "Digital Bug Centibit" and "Digital Bug Rhinosebus"), they have similar visual designs, and similar card effects revolving around Insect monsters and Xyz Summoning, but there are no cards with an effect that specifically affects cards with the "Digital Bug" name substring.
Unlike archetypes, which are most often explicitly intended to be built into proper Decks, series may or may not be glued comprehensively together, especially during the very early days of the game's history. More modern takes of series usually enable them to be built into proper Decks more reliably, not dissimilar to archetypes. This is done usually through supports that don't rely on name substrings, such as mentioning card(s) that glued them together, or supporting certain gimmicks that don't necessitate archetypal name substring usages, thus blurring the distinction between them and archetypes even further.
Series commonly, but not exclusively, comprise themed groups used by characters in the anime or manga. A group of cards may be a series in one media and an archetype in another. Examples of this include the Gorgonic and Red cards, which are both archetypes in the anime and manga, respectively, but lack archetypal support in the TCG/OCG. Also, a member of a series may also be a part of an archetype, an example being the Ultimate Insect series, whose members are all part of the "LV" archetype.
In Yu-Gi-Oh! Rush Duel, since there is a lack of a proper archetype name substring mechanic, all themes that appear in the game are exclusively played as series (even those that appeared as archetypes in the OCG/TCG like Dark Magician and Archfiend), a majority of which are based around using a specific Type, Attribute, and/or stat combinations. However, in "7 Theme Duel Tournament" style events, the Decks available for use are usually grouped under a proper archetype name substring mechanic that may also be linked to the Type or a specific stat. Examples: Include 15+ cards with “Necromaid” in their name in your Main Deck (where you can only include cards with “Necromaid” mentioned in their name) or Include 15+ LIGHT Machine monsters with 800 DEF in your Main Deck (where all the Monsters with this combination are related belong to Gradius in Rush Duels)