Translation guide
In Japanese, expressing 'one arm' depends on context: counting arms, describing a person with one arm, or referring to one side of the body. The most common way is 片腕 (kataude), but other expressions exist for specific situations.
Referring to a single arm, often in contexts like injury, amputation, or one-armed actions.
The standard word for 'one arm' when contrasting with having two. Used for people with one arm, or actions done with one arm.
彼は片腕を失った。
He lost one arm.
片腕で腕立て伏せをする。
Do push-ups with one arm.
Literally 'one of the two arms'. More explicit than 片腕, often used when specifying left or right.
片方の腕がしびれている。
One of my arms is numb.
Uses the counter 本 for long cylindrical objects. Emphasizes the count of one arm, but sounds a bit unnatural for body parts unless counting explicitly.
Avoid using this for general 'one arm' references; 片腕 is more natural.
彼は一本の腕で重い荷物を持ち上げた。
He lifted the heavy luggage with one arm.
Describing someone who has only one arm, either congenitally or due to amputation.
Literally 'one-arm person'. The most straightforward way to refer to a person with one arm.
彼は生まれつき片腕の人だ。
He is a person with one arm from birth.
A formal or literary term for 'one arm' or 'one-armed person'. Rare in everyday speech.
隻腕の剣士
a one-armed swordsman
Counting arms as objects, e.g., in anatomy, robotics, or when enumerating.
The counter 本 follows the noun. Used when counting arms explicitly.
ロボットには腕が一本しかない。
The robot has only one arm.
Using 'one arm' metaphorically to mean a trusted assistant or indispensable person.
Also means 'right-hand man' or 'trusted assistant'. Very common figurative use.
彼は社長の片腕として働いている。
He works as the president's right-hand man.
片腕 is the natural way to say 'one arm' in most contexts. 一本の腕 sounds like you are counting arms as objects, which is unusual for body parts. Use 片腕 for injuries, descriptions, and figurative meanings.
一つの腕 is not idiomatic. Use 片腕 or 片方の腕 instead.