Translation guide
How to express that something will happen or be done after a small number of days, typically 2–4 days from now.
The speaker refers to a point in time roughly 2–4 days in the future.
Neutral and common. Literally 'a few days later/after'. Used in both speech and writing.
数日後にまた来ます。
I'll come again in a few days.
結果は数日後にお知らせします。
We will inform you of the results in a few days.
The speaker refers to the time needed to complete something, meaning 'in the span of a few days'.
Neutral. Indicates that something can be done within a few days.
この仕事は数日で終わります。
This work will be finished in a few days.
The speaker refers to something that happens repeatedly with an interval of a few days.
Means 'every few days' or 'at intervals of a few days'.
数日おきに雨が降ります。
It rains every few days.
While 何日か後 (なんにちかご) can mean 'after some days', it sounds like 'after an unknown number of days' and is less natural for the fixed expression 'in a few days'. Use 数日後 or ２、３日後 instead.
✕ 何日か後に来ます。
I'll come after some days. (unnatural)
Very common in casual and spoken Japanese. Literally '2–3 days later'. Implies a short, indefinite wait.
２、３日後にもう一度電話します。
I'll call again in a few days.
Means 'within a few days'. Emphasizes that the action will happen sometime during the next few days.
数日のうちにご連絡します。
I'll contact you in a few days.
Formal/written. Means 'in the near future' or 'shortly', often used in business contexts. Can imply a slightly longer span than 'a few days'.
近日中に詳細をお送りします。
We will send you the details in a few days.
Casual/spoken. 'In 2–3 days'.
風邪は２、３日で治るよ。
A cold will get better in a few days.
More specific: 'every 2–3 days'.
２、３日おきにジムに行っています。
I go to the gym every few days.