Look - to look at something for a reason, with an intention.

 ‘Look at that strange man.’

‘Look at the pictures I took on holiday.’

 

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See -to ‘see’ something that comes into our sight that we weren’t looking for.

 ‘Did you see that bird? – I wasn’t looking for it,  it just appeared.

‘I saw you driving to work today.’

 

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Watch - to look at something carefully, usually at something which is moving.

 ‘Watch TV’- the TV doesn’t move, but you watch the moving images carefully.

‘Watch here you are going! You almost stepped on my foot!’