1.
one (long cylindrical object)
The counter reading for one of something long and thin, such as bottles, pens, trees, or roads.
ビールを一本ください。
Please give me one beer.
ペンが一本足りない。
One pen is missing.
道は一本だけだ。
There's only one road.
2.
ippon, full point (judo/martial arts)
A full point in judo or other martial arts that wins the match instantly.
一本を取った。
He scored an ippon.
見事な一本勝ちだった。
It was a splendid ippon victory.
審判が一本を宣告した。
The referee declared ippon.
3.
single-mindedness, one track
A focus on one thing, often used in compound expressions.
一本気な性格だ。
He has a single-minded personality.
芸の道一本で生きてきた。
I've lived by focusing solely on my art.
野球一本でやってきた。
I've devoted myself entirely to baseball.
一本 is the reading for "one" with the counter 本, used for long cylindrical objects.
COUNTER USAGE (Sense 1):
- ビール一本: one beer (bottle/can)
- 傘一本: one umbrella
- 木一本: one tree
- 電話一本: one phone call
JUDO USAGE (Sense 2):
- 一本: full point (instant win)
- 技あり: half point
- 一本勝ち: ippon victory
COMPOUND EXPRESSIONS (Sense 3):
- 一本気: single-mindedness, straightforwardness
- 一本道: single path, one-track
- 一本立ち: standing on one's own, independence