within

Từ điển Oxford Advanced Learner 8th

with·in preposition, adverb BrE [wɪˈðɪn] NAmE [wɪˈðɪn]
preposition
1. before a particular period of time has passed; during a particular period of time
• You should receive a reply within seven days.
• The ambulance arrived within minutes of the call being made.
•Two elections were held within the space of a year.
2. not further than a particular distance from sth
•a house within a mile of the station
• Is it within walking distance?
3. inside the range or limits of sth
• That question is not within the scope of this talk.
• We are now within range of enemy fire.
•He finds it hard to live within his income (= without spending more than he earns).
4. (formal)inside sth/sb
• The noise seems to be coming from within the building.
• There is discontent within the farming industry.
•Despite her grief, she found a hidden strength within herself.

Word Origin:
late Old English withinnan ‘on the inside’
 
adverb (formal)
inside
• Cleaner required. Apply within. (= on a sign)

Word Origin:
[within] late Old English withinnan ‘on the inside’