Convex vs. concave – which form is correct?

Convex or concave? Which word is correct? If you think that it is not your concern as it looks like they are only important for use in science and maths, this article is for you, as you can come across these terms in everyday speech when describing mirrors, contact lenses or eyeglasses.

Convex vs. concave – which one is correct?

It turns out that both convex and concave are correct. It is easy to mix them up, though, as they are correlative terms. They are both used as a noun or as an adjective and their meaning is also related. However, convex and concave differ in one small but important detail. Read the following section to find out what it is.

Convex vs. concave – what is the difference?

The words convex and concave describe a specific shape – the direction that an object curves. A convex shape is the opposite of a concave shape. Read the below sections with definitions of both words to make sure you are familiar with the difference.

Convex – the meaning

Convex is most commonly used as an adjective describing an outline or a surface that is curved or swelling out. A convex shape curves outward and its middle is thicker than its edges. If you still have problems of picturing it, think of an American football ball.

Concave – the meaning

Concave is mostly used as an adjective describing an outline or a surface that is curved in. As with convex, concave is most commonly used to describe processes linked to mirrors, lenses and reflection. You can also use concave for less scientific terms when describing, for example, the inside part of a bowl which is a concave shape; something that curves inwards like a crater or pothole or the cheeks of a very thin person.

Check out the following section to see how both words can be used in sentences.

Convex vs. concave – examples from the literature and press

Above us, the sails lose their stiff convex tone, and sag limp and lifeless.

Neal Shusterman, Challenger Deep

Fixed to the front of it was something that looked like a fencing mask, with the concave side outwards.

George Orwell, 1984

Some of the houses have facades that are either concave or convex, depending on what side of the street they’re on.

“Washington Post”, Nov 12, 2023