Quick answer
Causa produces an effect. Motivo explains an action. Razao gives reason or logic.
A reliable test is to identify the job of the word before translating from English.
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What each word does
causa
cause
Use causa for the factor that produces an effect or result.
motivo
motive or reason
Use motivo for the reason someone acts or the explanation for something.
razao
reason
Use razao for logic, justification, or a reason in argument.
How to choose
- causa: Choose causa if the sentence points to the factor that produces an effect or result.
- motivo: Choose motivo if the sentence points to the reason someone acts or the explanation for something.
- razao: Choose razao if the sentence points to logic, justification, or a reason in argument.
Examples
A causa do atraso foi a chuva.
The cause of the delay was the rain.
Qual foi o motivo da decisao?
What was the reason for the decision?
Voce tem razao.
You are right.
Common trap
Razao can also mean being right, as in voce tem razao.
Practice it in context
Pick one sentence from your real life and write it twice: once with causa, then once with motivo. If both versions feel possible, name the meaning shift.
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