Over is a preposition, adverb, adjective or prefix.
Over as a preposition
Over for movement and position
We use over to talk about movement or position at a higher level than something else:
A beautiful white bird flew over the lake.
With an umbrella over my head, I was able to protect myself from the midday sun.
We can also use over when talking about movement across a surface:
A small boat came over the lake and approached our cottage.
Shall we go over the road and see if there’s a bank on the other side?
Over and all over
We can use over, and the stronger form all over, when something is covering something:
You can buy a plastic cover to put over your computer if you’re worried about dust.
He had mud all over his face.
Over for periods of time
We can use over to refer to extended periods of time:
Over a period of three centuries, very little changed in the pattern of life for the poorest people.
What are you doing over the summer holidays? Are you going away?
Over with numbers
Over means ‘more than’ a particular number, or limit:
There were over 100 people at the lecture.
If your hand baggage weighs over 10 kilos, you must check it in.
She couldn’t enter the competition. She was over the age limit.
Over as an adverb
We can use over as an adverb to talk about movement above something or someone:
We were sitting in the garden and a huge flock of geese flew over. It was beautiful.
Over as an adverb can mean ‘to someone’s house’:
Would you like to come over and have dinner one evening? (to the speaker’s house)
Over and over (adverb phrase)
Over and over means ‘repeatedly’, ‘many times’. It often refers to things which people do not want to happen:
[adult to a little child]
Stop it! I’ve told you over and over not to play with the radio!
Over as an adjective: be over
We can use be over to mean ‘finished’, ‘at an end’:
We were so late that, when we got to the cinema, the film was over.
Over as a prefix
We can use over as a prefix to mean ‘too much’. We connect over to the word which comes after it, sometimes with a hyphen after over:
That new restaurant is overpriced if you ask me. (the meals are too expensive)
I didn’t enjoy the play. It was a student production, and everyone seemed to be overacting.
These are the main meanings of over but you will find other meanings and phrasal verbs with over in a good learner’s dictionary.
Over: typical errors
Over, when used with periods of time, refers to the period from start to finish, not to any one moment during that time:
I arrived during the afternoon.
I arrived over the afternoon.
Over as a prefix meaning ‘too much’ is connected to the word that comes after it, sometimes with a hyphen; we don’t write two separate words:
The nightclub was overcrowded.
The nightclub was over crowded.