noun
newly introduced word; new vocabulary item
Typically used in educational contexts for a word that appears for the first time in a lesson or textbook and needs to be learned.
今日の授業では新出語が10個あります。
In today's lesson there are ten new vocabulary words.
新出語をノートに書き写して覚えましょう。
Let's copy the new words into our notebooks and memorize them.
単語 is a general term for any word or vocabulary item, without the implication of being newly introduced.
Compound of 新出 (しんしゅつ, 'newly appearing') + 語 (ご, 'word'). The exact historical derivation is uncertain, but the meaning is transparent from its components.