Definition of “on” - Learner’s Dictionary

on

preposition uk us /ɒn/
SURFACE

A1 on a surface of something:

We put all of our medicine on a high shelf.
Ouch, you're standing on my foot!
PLACE

A2 in a particular place:

the diagram on page 22
I met her on a ship.
RECORDING/PERFORMANCE

A2 used to show the way in which something is recorded or performed:

What's on television tonight?
I bought the CD but you can buy it on cassette.
TOUCHING

B2 used to show what happens as a result of touching something:

I cut myself on a knife.
SUBJECT

B1 about:

MONEY/TIME

A2 used to show what money or time is used for:

I've wasted too much time on this already.
She spends a lot of money on clothes.
NEXT TO

B1 next to or along the side of:

The post office is on Bateman Street.
DATE/DAY

A1 used to show the date or day when something happens:

He's due to arrive on 14 February.
I'm working on my birthday.
USING

B1 using something:

I spoke to Mum on the phone.
I wrote it on my word processor.
AFTER

happening after something and often because of it:

The Prince was informed on his return to the UK.
TRANSPORT

A2 used to show some methods of travelling:

Did you go over on the ferry?
FOOD/FUEL/DRUGS

B2 used to show something that is used as food, fuel, or a drug:

I can't drink wine because I'm on antibiotics.
be on a committee/panel, etc

to be a member of a group or organization:

She's on the playgroup committee.
have/carry sth on you

to have something with you:

Do you have your driving licence on you?
be on me/him, etc informal

used to show who is paying for something:

This meal is on me.

(Definition of “on preposition” from the Cambridge Learner's Dictionary © Cambridge University Press)