millimetre

Word family

• metre
  nounA2
• centimetre
  nounA2
• millimeter
  nounA2
• micrometre
  nounB2

Synonym discussion

Sense: noun/1

Millimetre and millimeter mean exactly the same thing; the difference is only spelling, with millimetre used in British English and millimeter in American English. A centimetre is larger: one centimetre equals ten millimetres, so it is better for objects that are small but easy to see, such as a button or a coin. A metre is much larger and is used for room size, height, or distance across a street. A micrometre is far smaller and belongs to technical work such as biology or engineering. For everyday tiny measurements like paper thickness, cracks, or gaps, millimetre is the natural choice.

Common collocations

Etymology

Millimetre combines milli-, from Latin mille meaning 'thousand', with metre, from Greek metron meaning 'measure' by way of French mètre. The word was created in the metric system to name one thousandth of a metre. British English keeps the -metre spelling, while American English usually writes millimeter.