The meanings of the two words overlap, but there is still a distinct difference. Please review the words in English. If you just remember the Chinese translation, then they are virtually indistinguishable.
related, relative and relevant 三個「相關的」單詞
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1. be relative to
If something is relative to something else, it changes according to the speed or level of the other thing.
The amount of petrol a car uses is relative to its speed.
If something is relative to a particular subject, it is connected with it.
Are these documents relative to the discussion?
2. be relevant to
be connected with what is happening or being discussed
Education should be relevant to the child’s needs.
The two phrases overlap at times, but there is still a distinct difference. “Be relevant to" refers to something being directly relating to the subject or problem being discussed or considered. It could be important to the discussion.
“Be relative to" refers to something that is connected with a particular subject. It also used in comparison with somebody/something else.