occur
/əˈkɜː(r)/verb
1occurred, occurring
no obj., with adverbial happen; take place发生：the accident occurred at about 3.30p.m.
事故发生在下午3点30分左右。
1.1
- exist or be found to be present in a place or under a particular set of conditions存在; 出现：
radon occurs naturally in rocks such as granite.
氡自然存在于花岗岩等岩石中。
1.2
occur to
(of a thought or idea) come into the mind of (someone)（想法）产生：with clause it occurred to him that he hadn't eaten.他想到他还没吃东西。
词源
late 15th cent.: from Latin occurrere 'go to meet, present itself', from ob- 'against' + currere 'to run'.