Late is an adjective and an adverb, describing an event that happened after the correct time:
We had a late breakfast at 10:00.
(the usual time for breakfast is earlier, around 7-9 AM)
The bus arrived thirty minutes late.
(the bus arrived thirty minutes after the correct time on the schedule)
Avoid this common error: if you arrive late for an appointment, don't say "Sorry for late" or "Sorry for the late." The correct expression is "Sorry I'm late."
Delay is a noun and a verb, describing a cause for something to be late:
We were delayed by heavy traffic.
(the traffic caused us to be late)
The delay in the project was caused by a miscommunication.
(the miscommunication caused the project to fall behind schedule)
Postpone is a verb - it is when you choose to do something at a later time than planned. Usually "delay" involves factors beyond your control (like the traffic or weather), whereas "postpone" is a more conscious decision to change the schedule.
Three team members aren't available on Tuesday - let's postpone the meeting until Thursday.
My daughter got sick, so we postponed our camping trip until the following weekend.
Kids cant absorb too many rules without turning off completely. Forget arguing about little stuff like fashion choices and occasional potty language. Focus on the things that really matter that means no hitting, rude talk, or lying.