noun
word for word; one word at a time
Used adverbially to describe doing something carefully for each individual word, such as translating, explaining, or memorizing.
先生は一語一語ていねいに発音した。
The teacher pronounced each word carefully.
契約書を一語一語確認する。
I check the contract word for word.
Reduplication of 一語 (いちご, 'one word'), forming an adverbial noun meaning 'word by word'.