adjective

isosceles

eye-SOS-uh-leez

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Isosceles (adjective) means having at least two sides of equal length, said especially of a triangle or trapezoid. Example: “She drew an isosceles triangle with two sides exactly six centimetres long.”

adjective

Having at least two sides of equal length, said especially of a triangle or trapezoid.

"She drew an isosceles triangle with two sides exactly six centimetres long."

"The roof formed an isosceles shape when viewed from the street."

"Pupils were asked to find the angles of an isosceles triangle."

How to use isosceles

Learner’s notes

In plain EnglishIt describes a triangle (or similar shape) with two matching sides.

When to use it

It is a technical term used mainly in mathematics and geometry lessons.

Memory tip

Picture the two equal sides as the shape's matching legs, which is what the Greek root literally describes.

Trace the full origin ↓

Easily confused with

equilateral scalene

Common pairings

isosceles triangle isosceles trapezoid

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C2 · Advanced serendipity Fortunate discoveries made entirely by accident.

Gen Z slang rizz Charm — the ability to attract a romantic interest.

B2 · Intermediate empathy The capacity to share another person’s feelings.

C1 · Advanced nonchalant Casually calm and relaxed; unconcerned.

Internet slang delulu Delusional — believing something against the odds.

Etymology nostalgia Greek nostos “return home” + algos “pain”.

C2 · Advanced serendipity Fortunate discoveries made entirely by accident.

Gen Z slang rizz Charm — the ability to attract a romantic interest.

B2 · Intermediate empathy The capacity to share another person’s feelings.

C1 · Advanced nonchalant Casually calm and relaxed; unconcerned.

Internet slang delulu Delusional — believing something against the odds.

Etymology nostalgia Greek nostos “return home” + algos “pain”.

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Fill the gap

Can you complete this real example?

She drew an _____ triangle with two sides exactly six centimetres long.

Etymology

The word entered English from Latin isoscelēs, which itself came from Ancient Greek isoskelēs, meaning equal-legged. That Greek word was built from isos, meaning equal, and skelos, meaning leg.

Origin: Latin

Rhymes for isosceles

Angeles

See all rhymes for isosceles →

Frequently asked questions

What does isosceles mean?

It describes a shape, usually a triangle, that has at least two sides of equal length.

Is an equilateral triangle also isosceles?

Yes, a triangle with three equal sides can be treated as a special case of an isosceles triangle.

Where does the word isosceles come from?

It comes from Ancient Greek words meaning equal and leg, passed into English by way of Latin.

What is the meaning of isosceles?

"isosceles" (adjective) means having at least two sides of equal length, said especially of a triangle or trapezoid.