Concave and convex are opposite terms that describe the shapes of objects like mirrors and lenses. Concave refers to the shape of a circle’s inside that curves inward. Contrarily, convex refers to the shape of a circle’s outside that curves outward.
Also, concave and convex can be used as an adjective or a noun. As adjectives, they describe shapes that either curve inward (concave) or outward (convex). Meanwhile, as nouns, they are used to name specific things rather than tell an object’s shape.
Both words are commonly used as adjectives despite the terms concave and convex having adjective and noun usage. Hence, it’s uncommon to use them as a noun. Instead, we use them as adjectives to describe an object’s shape or surface by determining whether it curves inward or outward.
When to Use Concave
We use concave as an adjective or noun to describe the shape of an object or surface that’s hollowed or rounded inward. For example, the inside of a bowl.
Concave is commonly used in lenses, mirrors, or reflection. A concave mirror can make us look taller due as the light reflects back from it. Concave lenses are used in things like binoculars, telescopes, cameras, and eyeglass lenses.
A concave refers to any line or surface that curves inward as a noun. (E.g. This line is a concave.) An object with a concave shape curves inward. Examples are a spoon or a bowl. Moreover, its middle is thinner than the edges.
Concave as an Adjective
I bought eyeglasses with concave lenses to correct my nearsightedness.
People with myopia can have corrective glasses with concave lenses to bring their vision to normal.
She took a scoop of ice cream, leaving a concave mark; she couldn’t eat any more of it, though.
Concave as a Noun
The surface of the swimming pool is a concave.
All the lines are concave.
When to Use Convex
We use convex as an adjective or noun to describe an object or surface that curves or bulges outward. A convex refers to any line or surface curving outward as a noun. (E.g. This line is a concave.) An example of an object with a convex shape is a basketball or a baseball. Furthermore, its middle is thicker than the edges.
Like concave, convex is also used in lenses, mirrors, or reflection. A convex mirror can make us look smaller as the light reflects back from it. Convex lenses are used in things like eyeglasses, magnifying glasses, and microscopes.
Convex as an Adjective
You can observe that the convex shape of the air balloon is apparent.
This fall, I got a new Christmas tree; the warm light convex bulbs on it look like glowing suns under low brightness.
Convex lenses are used in eyeglasses to correct farsightedness.
Convex as a Noun
The rough surface toward the left is a convex.
When I take a closer look at the telescope, the mirror is a convex.
Concave vs. Convex: What’s the Difference?
The difference between concave and convex is that the former means curved inward, and the latter means curved outward. To distinguish which one to use, remember that concave has the word “cave” in it (similar to “caving in” literally) and means “hollowed or rounded inward.” Meanwhile, convex has the word “vex” in it (it is “vexing” that this word is hard to remember) and means “curved outward.”
Longman Dictionary of Contemporary English Online. (n.d.). Concave. Inhttps://www.ldoceonline.com/ dictionary. Retrieved March 11, 2022, from https://www.ldoceonline.com/dictionary/concave
Longman Dictionary of Contemporary English Online. (n.d.). Convex. Inhttps://www.ldoceonline.com/ dictionary. Retrieved March 11, 2022, from https://www.ldoceonline.com/dictionary/convex
Merriam-Webster. (n.d.). ‘Concave’ vs. ‘Convex’. In Merriam-Webster.com dictionary. Retrieved March 12, 2022, from https://www.merriam-webster.com/words-at-play/concave-vs-convex
Merriam-Webster. (n.d.). Concave. In Merriam-Webster.com dictionary. Retrieved March 12, 2022, from https://www.merriam-webster.com/dictionary/concave
Merriam-Webster. (n.d.). Convex. In Merriam-Webster.com dictionary. Retrieved March 12, 2022, from https://www.merriam-webster.com/dictionary/convex