core vocabulary; basic vocabulary
Refers to the set of most essential words in a language, often used in language education and linguistics.
In Japanese language education, it is important to first learn the core vocabulary.
基礎語彙 is similar but can emphasize foundational or basic vocabulary, while 基本語彙 is more common in pedagogical contexts.
Compound of 基本 (kihon, 'foundation, basis') and 語彙 (goi, 'vocabulary').