Translation: « J’ai besoin de me faire couper les poils. »
Why wrong: Hair is a non-count noun for masses that are too big to be counted. Hairs, when counted, mean poils. For more information, click here.
Correct it: If you mean chevelure, a mass, use hair, but if you mean individual strands you can count either that stand up on the head or that are elsewhere on the body, say hairs.
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