Definition

A unit used to measure how strongly a lens can bend light, which is calculated by taking the inverse of the distance from the lens to the point where it focuses light, measured in meters.

Example

The optometrist prescribed glasses with a diopter of -2.5 to correct my vision.

Conversation

I recently learned about how the diopter measures lens power.

Oh really? I didn’t know that!

Yeah, it’s interesting because it helps you understand how glasses work.

That makes sense! I guess that’s why my prescription has a diopter value.

Synonyms & Antonyms

Root Explanation

Diopter → It is formed from "di-" (meaning two) and "optere" (from Greek "optikos", meaning relating to vision). The word refers to a unit of measurement for the optical power of a lens, indicating how it bends light to focus on two points.

Memory Tip

Think of 'two' ('di-') points of focus in vision, which helps you remember that a diopter measures the optical power of a lens.

Visually Confused Words