inadvertent, fortuitous, anneal, side benefit

inadvertent : 의도치 않은, 뜻하지 않은

not ​intentional:All ​authors need to be ​wary of inadvertent ​copying of other people's ​ideas.
[작가들은 다른 사람의 아이디어를 의도치 않게 쓰는 것에 '
주의를 해야 한다.]
He inadvertently ​deleted the ​file.
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fortuitous : 뜻 밖의 행운인, 
(of something that is to ​your ​advantage) not ​planned, ​happening by ​chance:
The ​timing of the ​meeting is ​certainly fortuitous.
The ​collapse of ​its ​rivals was a fortuitous ​opportunity for the ​company.
We made a fortuitous ​escape.
The ​discovery of the ​files was fortuitous.
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annealto make ​metal or ​glass ​soft by ​heating and then ​cooling it ​slowly
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side effect <-------> side benefit(의도치 않은 이익)