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face
surface
mask (esp. a noh or kyogen mask)
「面」 has other readings with different meanings.
この問題には様々な面があると思う。
I think this problem has various aspects.
池の面に月が映り、夜風がわずかに波紋を立てていた。
The moon was reflected on the surface of the pond, and the night breeze stirred faint ripples.
彼の優しい面を知って印象が変わった。
My impression changed after knowing his kind side.