a male given name

one letter, one character

(idiomatic) unhesitatingly without dispute

(grammar) The monograde verb conjugation class, consisting of the two subclasses of 上(かみ)一(いち)段(だん)活(かつ)用(よう) (kami ichidan katsuyō, “upper-monograde conjugation”) and 下(しも)一(いち)段(だん)活(かつ)用(よう) (shimo ichidan katsuyō, “lower-monograde conjugation”)

(military) captain (Japanese Air Self-Defense Forces, Japanese Ground Self Defense Forces) / (military) lieutenant (senior grade) (Japanese Maritime Self-Defense Force)

city

all day

Alternative spelling of 一輪車 (“unicycle”)

Synonym of チアミン (chiamin, “thiamine”); vitamin B1

(informal) "not knowing even a millimeter": completely ignorant in regards to something