active vocabulary
Linguistics term for words a speaker actually uses, as opposed to words merely understood (passive vocabulary).
In second-language learning, it is important to increase one's active vocabulary.
理解語彙 is passive vocabulary (words one understands), while 使用語彙 is active vocabulary (words one actually uses).
Compound of 使用 (use) and 語彙 (vocabulary). The exact historical derivation is uncertain; the term is a modern linguistics calque.