/ ˌʌndəˈniːθ; NAmE -dərˈn-/ preposition , adverb , noun
■ preposition , adverb
1.
under or below sth else, especially when it is hidden or covered by the thing on top :
The coin rolled underneath the piano.
This jacket's too big, even with a sweater underneath.
2.
used to talk about sb's real feelings or character, as opposed to the way they seem to be :
Underneath her cool exterior she was really very frightened.
He seems bad-tempered, but he's very soft-hearted underneath.
■ noun
the underneath [ sing. ] the lower surface or part of sth :
She pulled the drawer out and examined the underneath carefully.
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WORD ORIGIN
Old English underneothan ; compare with beneath .