occur

1. (intransitive) To happen or take place.Examples: "The liftoff will occur in exactly twelve seconds."; "And no use for anyone to tell Charles that this was because the Family was in mourning for Mr Granville Darracott […]: Charles might only have been second footman at Darracott Place for a couple of months when that disaster occurred, but no one could gammon him into thinking that my lord cared a spangle for his heir."Synonyms: belimpintransitive

2. (intransitive) To present or offer itself.Examples: "I will write if the opportunity occurs."Synonyms: appear, arise, come upintransitive

3. (impersonal) To come or be presented to the mind; to suggest itself.Examples: "One little incident of my school days occurs to me as amusing."; "It occurred to him to tell me of the problem."; "Apparently it never occurs to them that you can't make rapid, drastic changes in the technology and the economy of a society without causing rapid changes in all other aspects of the society as well, […]"Synonyms: hitimpersonal

4. (intransitive, sciences) To be present or found.Examples: "The chemical monofluoroacetate occurs in all parts of Dichapetalum cymosum, and is responsible for its toxic effects."intransitive