for [Oxford Dictionary]
Having (the thing mentioned) as a reason or cause
‘I'd like to take her somewhere in the US or Europe as a surprise for her birthday.’
for [electronic dictionary]
=> used to show a reason or cause
She gave me a watch for my birthday.
[Longman ELC]
for= at the time of, on the occasion of
He bought his son a boat for his birthday.
We've invited our guests for 9 o'clock.
She's coming home for Christmas.
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I posted the definition of 'for' in dictionaries. The definition of 'for' seems to be different between longman and Oxford dictionary.
1. He bought his son a boat for his birthday.
2. He bought his son a boat on his birthday.
(Does #1 mean he did it on his birthday? Or before his birthday? Does 'for' mean 'at the time of' or 'Having (the thing mentioned) as a reason or cause')
3. She's coming home for Christmas.
4. She's coming home on/at Christmas.
(Does #3 mean #4? In #3, is she coming on the Christmas Day?)
5. He is going to buy many things for his winter vacation.
6. He is going to buy many things on his winter vacation.
(Does #5 mean that he will buy items to prepare for the winter vacation, before the winter vacation? Or does #5 mean #6? Does 'for' mean 'at the time of' all the time or 'used to show a reason or cause'?)
4 answers
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1. He bought his son a boat for his birthday.
2. He bought his son a boat on his birthday.
(Does #1 mean he did it on his birthday? No Or before his birthday? yes
Does 'for' mean 'at the time of' or 'Having (the thing mentioned) as a reason or cause') "On" means at the time; "for" (in this case) means as a reason or cause.
3. She's coming home for Christmas.
4. She's coming home on/at Christmas.
(Does #3 mean #4? In #3, is she coming on the Christmas Day?)
"For" or "at" normally means just before Christmas; "on" means on that day.
5. He is going to buy many things for his winter vacation.
6. He is going to buy many things on his winter vacation.
(Does #5 mean that he will buy items to prepare for the winter vacation, before the winter vacation? Yes Or does #5 mean #6? No
Does 'for' mean 'at the time of' all the time or 'used to show a reason or cause'?) shows a reason or cause
1 "for his birthday" means on the occasion of his birthday. The boat could have been purchased at any time, but was in honor of the birthday. 2 "On his birthday" means the purchase was made on that date. 3 & 4, again "for" or "at" means before, during, even after the 25th of December, but the trip home will be prompted by the occasion. "at" Christmas means the same thing, on or around the 25th. "on" Christmas means specifically on the 25th. 5, "for his winter vacation" implies in preparation for the vacation. If he's going to the beach in Australia, he might buy swimming trunks, new shirts, etc., in advance. 6. "on his winter vacation" means while he is away on vacation (souvenirs, items not available at home, etc.).
Then what does #7 mean #8 or #9?
7. What are you going to do for your winter vacation?
8. What are you going to do to prepare for your winter vacation, before the winter vacation?
9. What are you going to do on/duriong your winter vacation?