Translation guide
The English phrase 'one thing' is used to introduce a single point, contrast, or exception. In Japanese, it is rarely translated literally. Instead, use phrases like 一つ (hitotsu) for counting, 一つだけ (hitotsu dake) for 'just one thing', or patterns like 一つ言えるのは (hitotsu ieru no wa) for 'one thing I can say is'. Often, the concept is expressed through sentence structure rather than a direct equivalent.
To say 'one thing (I want to say/mention) is...' or 'there is one thing...'
Literally 'one thing I can say is'. Used to introduce a single important point or opinion.
一つ言えるのは、彼は誠実だということだ。
One thing I can say is that he is sincere.
Polite way to say 'let me say just one thing'. Used when you want to interject or add a point.
一つだけ言わせてください。その計画は危険です。
Let me say just one thing. That plan is dangerous.
Means 'there is one thing that bothers me' or 'one thing I'm curious about'. Natural for raising a concern.
一つ気になることがあるんですが。
There's one thing I'm wondering about.
To say 'just one thing', 'only one thing', or 'one thing (as opposed to many)'
Means 'just one thing' or 'only one'. Used when limiting to a single item.
欲しいものは一つだけです。
There's just one thing I want.
一つだけ質問があります。
I have just one question.
The basic counter for one thing. Can be used in many contexts, but often needs particles or context to mean 'one thing' specifically.
一つください。
One, please. (e.g., when ordering)
To say 'one thing is X, another is Y' or 'for one thing... for another...'
Pattern for 'one thing is ~, another thing is ~'. Used to list or contrast two items.
一つは値段で、もう一つは品質です。
One thing is the price, and another is the quality.
Means 'for one thing, ... and also ...'. Slightly more formal or written.
一つには時間がないし、またお金もない。
For one thing, I don't have time, and also I don't have money.
To request or ask for a single item or piece of information
Common phrase meaning 'I have a favor to ask' or 'I have one request'. Polite and natural.
一つお願いがあるんですが。
I have a favor to ask.
Means 'please tell me one thing'. Used when you want to ask a single question.
一つ教えてください。駅はどこですか？
Tell me one thing. Where is the station?
Do not translate 'one thing' as 一つのこと (hitotsu no koto) in most contexts. It sounds unnatural and overly literal. Use the patterns above instead.
When 'thing' refers to an abstract concept or matter, you can use こと (koto) instead of 物 (mono). For example, 一つのこと (hitotsu no koto) can mean 'one matter', but it is less common than the patterns above.