What is the difference between 'win' and 'gain'?

[salsa]

Test No. incompl/elem-2 "Money accepted", question 3

One day I hope I shall ......... the lottery.

(a) gain
(b) collect
(c) reach
(d) win

Test No. incompl/elem-2 "Money accepted", answer 3

One day I hope I shall win the lottery.

Correct answer: (d) win

Your answer was: incorrect
One day I hope I shall gain the lottery.
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A3 correct sentence:
One day I hope I shall win the lottery.

Correct answer: (d) win

Your answer was: incorrect
your sentence:
One day I hope I shall gain the lottery.

hi,
can you tell me, when i should use gain and when win.
thank for your help!

[Torsten]

You can gain weight, a profit, an experience etc. and you can win a prize, the lottery, a game etc.
Gain implies that you make an effort to achieve a goal while win often (not always) means you get something by accident (exception: to win a game or match in sports).
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Test Of English for International Communication
TOEIC Preparation & TOEIC Vocabulary

[Makram145]

Dear Torsten,

I'm in correct answer but I get it from your sit wrong and you said correct answer is win that is my answer