noun
different character; other character
Refers to a character that is not the same as another, often in the context of distinguishing kanji or kana.
この漢字は異字だけど、意味は似ている。
This kanji is a different character, but the meaning is similar.
noun
variant character; different written form
Used for a character that is a variant or alternative form of another, such as traditional/simplified or old/new forms.
「国」と「國」は異字の関係にある。
「国」 and 「國」 are variant characters of each other.