numeric, prefix
one; 1
The cardinal number one. Also used as a prefix in counting or numbering. Legal variants 壱, 弌, 壹 are used to prevent alteration.
一から十まで数えてください。
Please count from one to ten.
一ページ目を開いて。
Open to the first page.
noun which may take the genitive case particle 'no', suffix
Used as a suffix or with の to mean the best or top in a category. Often in compounds like 日本一 (Japan's best).
彼はクラスで一の成績だ。
He has the best grades in the class.
この店のラーメンは世界一おいしい。
This shop's ramen is the most delicious in the world.
noun
Refers to the start or origin of something. Often used in set phrases like 一からやり直す.
一からやり直そう。
Let's start over from the beginning.
一を聞いて十を知る。
Hearing one thing, understand ten. (A wise person grasps the whole from a part.)
noun, used as a prefix
Used as a prefix before a noun to mean 'a single' or 'one of many'. Common in compounds like 一石二鳥.
一つのりんごを食べた。
I ate one apple.
一石二鳥だ。
It's killing two birds with one stone.
noun
In card games, the ace. Cross-referenced with エース.
See also: エース
一のカードを出した。
I played the ace.
noun
bottom string (shamisen, etc.)
The first (lowest-pitched) string on a shamisen or similar instrument.
三味線の一の糸を張り替える。
Replace the bottom string of the shamisen.