Nomi

"Nomi" （「のみ」） is a special term that refers to some monsters. If a monster is a "Nomi monster", then it means that the monster cannot be Normal Summoned or Set. You can identify a Nomi monster because it will have, "This card cannot be Normal Summoned or Set. This card cannot be Special Summoned except by..." in its text. It can neither be Special Summoned except by fulfilling a special requirement. Examples of Nomi monsters include "Armed Dragon LV10", "Doom Dozer", "Dark Armed Dragon", "Raviel, Lord of Phantasms", and all Elemental Hero Fusion monsters. It is also to be noted that the Special Summoning of these cards can only be done while the card in question is in the owner's hand unless stated otherwise in card text.

There is also a type of monster called "Special Summon-Only".