(plural, plural-only) A school punishment in which a student must repeatedly write out a line of text related to the offence (e.g. "I must be quiet in class") a specified number of times; the lines of text so written out.
If you don't behave I'll give you lines
I had to write out 200 lines
(US, plural, plural-only) The reins with which a horse is guided by its driver.
(plural, plural-only) A certificate of church membership.