on

In the state of being active, functioning or operating.

• All the lights are on, so they must be home.

Happening; taking place; being or due to be put into action.

• We had to ration our food because there was a war on.
• Some of the cast went down with flu, but the show's still on.
• That TV programme that you wanted to watch is on now.

Of a person, used to express agreement to or acceptance of a proposal or challenge made by that person; most commonly with subject "you" (see you're on).

• "Five bucks says the Cavs win tonight." ―"You're on!"
• If he wants a fight, he's on!

Fitted; covering or being worn.

• Your feet will soon warm up once your socks are on.
• I was trying to drink out of the bottle while the top was still on!

Of a stated part of something, oriented towards the viewer or other specified direction.

• The photograph shows the UFO side on.
• edge on, side on, end on, face on

Acceptable, appropriate.

• It's not fair to do that – it's just not on.

Possible; capable of being successfully carried out.

• Climbing up that steep ridge isn't on. We'll have to find another route.
• He'd like to play the red next to the black spot, but that shot isn't on.

Available; remaining.

• Smith is 25 points ahead with only 23 on.

Having reached a base as a runner and being positioned there, awaiting further action from a subsequent batter.

Within the half of the field on the same side as the batsman's legs; the left side for a right-handed batsman.

• The captain moved two fielders to the on side.
• Ponsonby-Smythe hit a thumping on drive.

Of a ball, being the next in sequence to be potted, according to the rules of the game.

• If the player fails to hit the ball on, it's a foul.

Acting in character.

Performative or funny in a wearying manner.

• He always has to be on, it's so exhausting.

Menstruating.

To an operating state.

• turn the television on

So as to cover or be fitted.

• The lid wasn't screwed on properly.
• Put on your hat and gloves.

Along, forwards (continuing an action), onwards.

• The policeman moved the tramp on.
• Drive on past the railway station.
• From now on things are going to be different.

In continuation, at length.

• and so on
• He rambled on and on.

Later.

• Ten years on, nothing had changed in the village.

Of betting odds, denoting a better-than-even chance. See also odds-on.

• That horse is twenty-to-one on, so you need to stake twenty pounds just to win one pound.

Of a ball, into a pottable position.

• The black was previously unavailable, but in potting that red, he's now pushed the black on.

Indicating position or location. Positioned at the upper surface of, touching from above.

• A vase of flowers stood on the table.
• Please lie down on the couch.
• The parrot was sitting on Jim's shoulder.

Positioned at the upper surface of, touching from above.

• A vase of flowers stood on the table.
• Please lie down on the couch.
• The parrot was sitting on Jim's shoulder.

Positioned at or resting against the outer surface of; attached to.

• He had a scar on the side of his face.
• There is a dirty smudge on this window.
• The painting hangs on the wall.

Covering.

• He wore old shoes on his feet.

At or in (a geographical location or position).

• The lighthouse that you can see is on the mainland.
• The suspect is thought to still be on the campus.

At (a relative spatial position).

• We live on the edge of the city.
• on the left, on the right, on the side, on the bottom

Near; adjacent to; alongside; just off.

• The fleet is on the American coast.
• Croton-on-Hudson, Rostov-on-Don, Southend-on-Sea

Aboard (a mode of transport, especially public transport, or transport that one sits astride or uses while standing).

• on a bus, on a train, on a plane, on a ferry, on a yacht
• on a bicycle, on a motorbike, on a horse, on a scooter

In the direction of (some part of one's vessel), to within 45 degrees.

• A ship was sighted on the port quarter.
• on the bow; on the starboard beam

Expressing figurative placement, burden, or attachment.

• All of the responsibility is on him.
• I put a bet on the winning horse.

Denoting physical contact or interaction with an object, such as impact or application of force. With verbs describing an action of pushing, pulling, pressing, etc., designates the thing to which force is applied.

• tug on the rope; push hard on the door
• I stubbed my toe on an old tree stump.
• I caught my fingernail on the door handle.

With verbs describing an action of pushing, pulling, pressing, etc., designates the thing to which force is applied.

• tug on the rope; push hard on the door

With verbs describing an action of hitting, rubbing, scratching, binding against, etc., designates the thing impacted or contacted.

• I stubbed my toe on an old tree stump.
• I caught my fingernail on the door handle.
• The rope snagged on a branch.

Denoting performance or action by contact with the surface, upper part, or outside of anything By means of; with.

• to play on a violin or piano

Supported by (the specified part of itself).

• A table can't stand on two legs.
• After resting on his elbows, he stood on his toes, then walked on his heels.

At (a certain value or level).

• The Tories are on twenty-five percent in this constituency.
• The blue team are on six points and the red team on five.

At (a certain position within a sequence).

• I'm on question four.

At or during the date or day of.

• Born on the 4th of July.
• On Sunday I'm busy. I'll see you on Monday.
• Can I see you on a different day?

At (a given time after the start of something).

• Smith scored again on twelve minutes, doubling Mudchester Rovers' lead.

At (an instant or cusp).

• on the stroke of midnight; on the "B" of "Bang!"
• on the point of leaving; on the verge of giving up

To switch on.

• Can you on the light?

Without. (Can we add an example for this sense?)

In the Japanese language, a pronunciation, or reading, of a kanji character that was originally based on the character's pronunciation in Chinese, contrasted with kun.

• Most kanji have two kinds of reading, called "on" and "kun".