How to say "millimeter" in Japanese

• ミリメートルCommon
  nounThe full form of the unit name, matching English 'millimeter' exactly. Use it whenever you want the complete unit name; ミリ is simply its abbreviation, so the two are interchangeable in meaning.
  この定規じょうぎにはミリメートルの目盛めもりがある。↗

  This ruler has the scale in millimeters.
• ミリJLPT N2approx.Common
  nounA common abbreviation of ミリメートル, meaning exactly the same unit. This is simply the short form: pick it when brevity matters, and there is no difference in what is being measured.
  目めの前まえで繰り広くりひろげられるやり取とりは、俺おれが入り込はいりこむ隙すきなんて一いちミリもない。↗

  The exchange unfolding in front of my eyes had not a single millimetre of a gap in which for me to slip.

Both words name the same unit, one thousandth of a metre: 「ミリメートル」 is the full form and 「ミリ」 its common abbreviation, so the choice depends only on whether you want the complete unit name or the short one.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• ミリメートルmillimeter
• ミリmillimetre