concave
/'kɔn'keiv/
Definition
- Adjective:
- Curving inward: Having a surface or shape that curves inward, like the interior of a bowl or a cave. The opposite of convex.
Usage
- The word "concave" is used to describe surfaces, lenses, mirrors, or shapes that are curved inward.
- It is often used in contrast with "convex" (curving outward).
- Common in scientific, technical, and everyday descriptions of form.
Examples
- Adjective:
- The inside of a spoon is concave.
- A concave lens causes light rays to spread out.
- The land formed a concave basin where water collected.
Advanced Usage
- "Concave up/down": In mathematics (calculus), a function's graph is described as concave up (shaped like a U) or concave down (shaped like an ∩).
- The parabola y=x² is concave up.
- "Concave polygon": In geometry, a polygon where at least one interior angle is greater than 180°, causing the shape to "cave in."
- A star shape is often a concave polygon.
Variants and Related Words
- Concavity (n): The state or quality of being concave; an inward curve or hollow.
- The concavity of the mirror distorted the reflection.
- Concaved (adj, rare): Made concave; hollowed.
- The concaved surface of the ancient shield.
Synonyms
- Hollow: Having a hole or empty space inside; sunken.
- Incurved: Curved inward.
- Scooped: Hollowed out like a scoop.
Antonyms
- Convex: Having a surface or shape that curves outward.
- Protuberant: Bulging outward.
Related Phrases/Compounds
- Concave mirror: A mirror with a reflecting surface that curves inward, used to focus light.
- Dentists use concave mirrors to see a magnified image of teeth.
- Concave slope: In geography, a slope that becomes steeper downhill.
Adjective
-
curving inward
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