Diameter

How to spell diameter

8 letters · 4 syllables

How to pronounce diameter

Say the part in capitals loudest.

What does diameter mean?

1. nounThe length of a straight line passing through the centre of a circle or sphere from one side to the other.

Diameter in a sentence

• The pipe has a diameter of twelve centimetres.

• Engineers measured the diameter of the tunnel before fitting the lining.

Where does diameter come from?

Language of origin: Greek

The word comes from the Greek diametros, meaning 'the measure across', which combined dia 'across or through' with metron 'a measure'. The Greeks used it for the straight line drawn across a circle through its centre, dividing it into two equal halves. It passed into Latin as diametrus and then into English through Old French in the late 1300s, when geometry texts were being translated and studied. The metron element is the same root that gives us 'metre', 'thermometer', and 'perimeter', so the word literally announces itself as a kind of measurement. The main spelling trap is that final '-meter' ending and the unstressed middle syllables, which a writer can easily blur when sounding the word out.

How the word is built

• dia- (across, through)
• meter (from metron: measure)