related term; associated word
Refers to a word that is semantically or thematically related to another word, often used in dictionary or thesaurus contexts.
In the dictionary, 'wave' and 'ship' are listed as related terms for 'sea'.
対義語 means 'antonym', a word with an opposite meaning, whereas 関連語 is not limited to opposites.
Compound of 関連 (kanren, 'relation') + 語 (go, 'word').