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concave

UK/ˈkɒn.keɪv/US/ˈkɑn.keɪv/
adjectiveC1Rare in speech; mostly a word you read · #13,014 of 15,258mostly written

Concave means curving inward, like the inside of a bowl. A concave lens, a concave mirror, the surface is slightly concave.

Its opposite is convex, and the two are constantly confused. The trick that works is the cave: a concave surface has a cave in it, which curves away from you. In optics, a concave lens spreads light out and is used to correct short sight; a concave mirror focuses it. The pair is also used in economics and mathematics for the shape of a curve, where it has a precise meaning and no bowls at all.

Definitions of concave

  1. 1adjectiveconcaveCurving inward, like the inside of a bowl.C1

    “The mirror is concave and turns everything upside down.”

    synonyms: hollow, dished

concave is a curved shape.

Where it comes from

Latin concavus is con-, thoroughly, plus cavus, hollow — the same root as cave and cavity. Concave is literally thoroughly hollow, which makes the cave mnemonic an etymology rather than a trick.

  1. Proto-Indo-European

    *ḱewh₁-

  2. Latin

    concavus

  3. Old French

    concave

  4. Middle English

    concave

  5. English, today

    concave

From Middle English concave, from Old French concave, from Latin concavus.

Etymology from Wiktionary, CC BY-SA

Practised in Light & Shadow, Shapes & Lines

Practise this word

concave in the wild

  • Equivalently, a concave function is any function for which the hypograph is convex.

    Concave function

  • The class of concave functions is in a sense the opposite of the class of convex functions.

    Concave function

  • Other types of ceiling include the cathedral ceiling, the concave or barrel-shaped ceiling, the stretched ceiling and the coffered ceiling.

    Ceiling

  • One can view these features as concave by viewing the image upside-down.

    Convex and Concave

  • The compound molding with the concave cavetto below and the convex ovolo above is termed cyma reversa.

    Ovolo

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From Wikipedia, CC BY-SA 4.0. These sentences were written by other people about their own subjects; they are here to show the word at work, not as anybody’s opinion.