Other forms: diameters
The diameter is the straight line across a circle through its centre. The diameter of the pipe, four centimetres in diameter, measure the diameter.
It is twice the radius, and the circumference is the diameter times pi. In diameter is the standard phrase for stating a width: about nine metres in diameter. Pipes, cables and lenses are all specified by diameter. Note that a chord is any line across a circle and a diameter is the longest possible one; and that diameter is used loosely of any roughly round thing.
1noundiameterThe straight line across a circle through its centre.
“The pizza was so big that its diameter was wider than the table.”
diameter is a measurement across.
Greek diametros is dia-, across, plus metron, a measure — the measure across. The same metron gives metre, thermometer and geometry, and the same dia- gives diagonal and diagnosis.
Latin
diametros
Old French
diametre
English, today
diameter
Built from
From Old French diametre, from Latin diametros. From Old French diametre (French diamètre), from Latin diametros, from Ancient Greek διάμετρος (γραμμή) (diametros grammē, “line measuring across”), from διά (“across”) + μέτρον (“measure”). by surface analysis, dia- + -meter.
Etymology from Wiktionary, CC BY-SA