noun
10th day of the month
Used for the tenth day of any month. Common in dates, appointments, and deadlines.
会議は１０日に行われます。
The meeting will be held on the 10th.
来月の十日は金曜日です。
The 10th of next month is a Friday.
noun
Refers to a period of ten days. Often used with counters or in expressions like 十日間.
この仕事は十日かかる。
This work takes ten days.
十日間の旅行を計画している。
I'm planning a ten-day trip.
十日間 explicitly specifies a duration of ten days, while 十日 can mean either the date or the period depending on context.
Combination of 十 (ten) and 日 (day), with the reading とおか derived from the native Japanese counting system.