pronoun
1
BAD : I had the whole beach for my own.
GOOD : I had the whole beach to myself.
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Own (= belonging to you, or only to be used by you) is used either in front of a noun, or in the phrase of your own: 'I wish I had my own car.' 'I wish I had a car of my own.'
have sb/sth (all) to yourself = be the only person or people in a place, using something, talking to someone, etc: 'After the children had gone, we had the house all to ourselves.'
2
BAD : He's decided to resign and work for his own.
GOOD : He's decided to resign and work for himself.
BAD : They want everything for their own.
GOOD : They want everything for themselves.
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do/want sth for yourself (NOT for your own ): 'He's kept all the money for himself.'
3
BAD : I didn't have a room for my own but had to share one.
GOOD : I didn't have a room of my own but had to share one.
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of your own (NOT for ): 'Timothy has now decided that he wants a bicycle of his own.'
4
BAD : I now have enough money to buy an own car.
GOOD : I now have enough money to buy my own car.
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Own always follows my/her/their/Jill's etc (NOT an ) 'their own children', 'her own flat', 'Tina's own radio'.