noun, noun which may take the genitive case particle 'no'
class period; school period
Specifically a scheduled class period in a school timetable. Often used with numbers: 1時限目, 2時限目, etc.
1時限目は数学です。
The first period is math.
We have gym class in the 3rd period.
時限ごとに教室が変わる。
The classroom changes each period.
noun, noun which may take the genitive case particle 'no'
time period; time limit
Broader sense of a fixed division of time or a deadline. Less common than the school-period sense; often seen in formal or technical contexts.
この作業には時限が設けられている。
A time limit has been set for this task.
Today we have two consecutive periods of class.
A time limit has been set on this special measure.
期限 means 'deadline' or 'expiration date', focusing on the end point, whereas 時限 refers more broadly to a bounded time period or limit.
コマ is a casual, spoken word for a class slot (especially at universities), while 時限 is the more formal term used in official timetables.
時限 is the more formal, written term for a class period, while 限 is the casual counter suffix attached directly to numbers (2限) in everyday student speech.
次元 (a dimension or level) and 時限 (a time limit, or a school period) are pronounced identically but have completely unrelated meanings.
nth period; nth class period
time-limited strike
time fuze; time fuse; time detonator
time-limited measure; temporary measure
time bomb
Compound of 時 (time) and 限 (limit, bound). The meaning 'school period' developed from the idea of a bounded time slot.