concave

Meanings

1. 1
   adj

   curved inward, like the inner surface of a bowl or sphere

   The satellite dish has a concave surface that focuses incoming signals.

2. 2
   adj

   in geometry, having an inward angle or indentation

   The arrowhead is a concave polygon because one interior angle exceeds 180 degrees.

3. 3
   adj

   of a mathematical function, having a graph whose chords lie below or on the graph

   The logarithm is a concave function over the positive real numbers.

From Middle English concave, through Old French concave, from Latin concavus ("hollow, arched inward"), formed from con- (an intensive prefix) + cavus ("hollow"). The core image of a hollowed or inward-curving surface has remained stable in English.

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