on the contrary反而 هو adverb ("instead, on the contrary") يقع قبل الفعل داخل جملة واحدة. opposite相反 هو adjective / conjunction بمعنى "(the) opposite" — يربط أو يفتح جملة، أو يصف شيئاً بأنه معاكس.
eating吃fruit水果not only不但no没benefit好处instead,反而has有harm坏处
Eating fruit not only does no good — instead it does harm.
my我的idea想法跟his他the opposite相反。
My idea is the opposite of his.
Remember: on the contrary反而 = an ADVERB ("instead," before the verb), marking a contrary RESULT; opposite相反 = "the opposite" (with / and跟…opposite相反, or opposite相反,… "on the contrary). One does a job inside the clause; the other names or links an opposite.
انتبه
- You can't swap them: on the contrary反而to have / there is有harm坏处 ✓ (adverb), with / and跟he / him他opposite相反 ✓ (adjective) — but not with / and跟he / him他on the contrary反而.