I have seen a sentence in book

Bacteria are important to human health

I have searched on stackexchange

And according to that answer -

To is used as : It is important to me

For is used as: It is important for my health.

So, as per above answer, it should be Bacteria are important for human health

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    There's a strong tendency to favour are important to X where X is some kind of "conscious entity" (such as me, in that link), because in such contexts we can interpret the statement as meaning X thinks that something is important..., Commented May 10, 2019 at 12:51
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    ...but if X is just an abstract concept such as health, as can be seen from that link, there's no significant tendency to prefer one preposition over the other, so your usage distinction isn't quite correct. Commented May 10, 2019 at 12:53

2 Answers 2


The cited answer does cover this, and you do answer your own question. "Importance" is a measure of value and therefore relative. It does not mean the same as, for example, "vital". "Important to me" means important from your perspective.

I feel your example is correct because bacteria are important from a human health perspective. They are not vital for life, but important to it.


"Important to" suggests that something is important to someone as a value.

This house is important to me (It's more emotional, like "I feel this house is important to me" or "it means a lot to me").

"Important for" suggests that something is important for something or someone as a need.

This house is important for me...or for you..or for him (It's more rational, like "I understand that this house is important for someone's survival.")

See also this and this answer.

So, I would say "Bacteria are important for human health."

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