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.
The first period is math.
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.
A time limit has been set for this task.
We have gym class in the 3rd period.
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.
Compound of 時 (time) and 限 (limit, bound). The meaning 'school period' developed from the idea of a bounded time slot.