在 + Time + 内 (within a span)
"Within (a span of time)"
- at / in在 + Time + inside内 = "within (a period)".
- at / in在三天inside内to complete完成 = "finish within three days."
- inside内 closes off the time window.
at / in在 + Time + inside内
- at / in在…inside内 sets the deadline-window for the action.
please请within在three days三天within内finish完成。
- at / in在三天inside内to complete完成 = "finish within three days."
Explore
Correct or broken?
在 + span + 内 draws the deadline box: within three days, inside the year.
Practice
Finish within three days: 请在三天 ____ 完成。
在 + Time + 内 = within: 在三天内完成.
Practice
以内 can be used similarly (三天以内).
Yes — 三天内 / 三天以内 both mean “within three days”.
Recap
Key idea
- at / in在 + Time + inside内 — "within (a span of time)"
- at / in在三天inside内 · at / in在一年inside内
- within以内 works similarly; inside内 closes the window
Read the full reference: HSK 5 grammar — Sentence patterns.
Practice
在一年内 means…
内 closes the time window: within that span.