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English definition of “or”

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or

conjunction  /ɔr, ər/ us  

or conjunction (POSSIBILITIES)

used to connect different possibilities: Is today Tuesday or Wednesday? You can get that blouse in blue, gray, or white. There were ten or twelve people in the room (= approximately that number of people). We’d better make a decision soon or the whole deal will fall through. After a negative verb, or can also continue the negative meaning of the verb: He won’t eat meat or fish (= and will not eat fish either).

or conjunction (EXPLAIN)

used to show that a word or phrase means the same as, or explains or corrects, another word or phrase: Photons, or individual particles of light, travel huge distances in space. Things were going well, or seemed to be, but the relationship had already begun to change.
Idioms
(Definition of or conjunction from the Cambridge Academic Content Dictionary © Cambridge University Press)
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