Translation guide
The English word 'one' has several distinct uses: as a number, a pronoun, and in various fixed expressions. This guide covers the most common ways to express these meanings in Japanese, from counting to referring to people or things in general.
Expressing the number one in counting, quantities, or identification.
The basic number 'one'. Used in counting, math, and when stating the number itself. Read as いち in most contexts, but can also be ひと in native Japanese counting.
The native Japanese counter for one thing. Used for generic objects when no specific counter is needed.
りんごを一つください。
One apple, please.
Referring to a single, unspecified person or thing, often in contrast to others.
Used for 'one' as a pronoun for things. Can mean 'one thing' or 'one of them'.
どれがいい？一つ選んで。
Which one is good? Pick one.
Used for 'one person'. Note that it's read ひとり, not いちにん.
Means 'one (of two)' or 'one side'. Often used in contrasts.
Making general statements about people, similar to 'you' or 'people' in English.
Japanese often omits the subject when making general statements. The impersonal 'one' is usually not translated directly.
そんなことは言わない。
One doesn't say such things.
The word for 'person' or 'people' can be used to mean 'one' in general statements.
人は見かけによらない。
One can't judge by appearances.
Means 'human being'. Used in more philosophical or general contexts about human nature.
Expressing that two things are the same or identical.
The most common way to say 'the same one'. Can be used as an adjective or adverb.
それと同じものをください。
I'll have the same one as that.
Indicating that something is a member of a category.
Literally 'one of ~'. Used to say something is one of a group.
これは私の趣味の一つです。
This is one of my hobbies.
Used for people: 'one of the (people)'. Read ひとり.
彼はチームの一人です。
He is one of the team.
Emphasizing that there is just one, no others.
Means 'only' or 'sole'. Often used in formal or written contexts.
これが唯一の方法です。
This is the one and only way.
Emphatic 'just one'. More colloquial than 唯一.
チャンスはたった一つだ。
There's only one chance.
Used in time expressions to mean a certain unspecified time.
Means 'a certain' or 'one'. Used before nouns like 日 (day) or 時 (time).
ある日、突然彼が現れた。
One day, he suddenly appeared.
English often uses 'one' to avoid repeating a noun (e.g., 'the red one'). In Japanese, you usually just use the noun again, or omit it if clear from context. Saying '赤いの' (the red one) is possible in casual speech, but overusing の as a pronoun can sound unnatural.
Japanese uses counters for different types of objects. 'One' changes form depending on what you're counting: 一つ (generic), 一人 (people), 一本 (long objects), 一枚 (flat objects), etc. Learn the most common counters early.
一つしかありません。
I only have one.
I'll go alone (by myself, as one person).
一方は赤、もう一方は青です。
One is red, the other is blue.
人間は一人では生きられない。
One cannot live alone.