What is 0.1 cm called

0.1 cm (one-tenth of a centimeter) equals 1 millimeter exactly, as the metric system defines 1 cm = 10 mm. There's no special name for 0.1 cm—it's simply expressed as "one millimeter" or "1 mm" in standard practice. The metric prefix system provides dedicated names for powers of ten (kilo- = 1,000×, centi- = 0.01×, milli- = 0.001×, micro- = 0.000001×), making fractional nomenclature like "one-tenth centimeter" unnecessary since "millimeter" already describes this quantity.

In dimensional specifications and engineering practice, measurements are expressed using the most appropriate metric unit to avoid decimal points when possible: use 1 mm rather than 0.1 cm, 500 mm rather than 0.5 m, 5 km rather than 5,000 m. This convention reduces transcription errors, simplifies mental arithmetic, and maintains clearer communication in technical documentation. The relationship 1 cm = 10 mm makes conversions between these units trivial by moving decimal points one position. For anyone familiar with rulers, each millimeter represents the smallest standard division between centimeter marks. Understanding that "0.1 cm" is simply another way of expressing "1 mm" prevents unnecessary confusion when encountering different unit representations of the same physical dimension—both are correct, though millimeter notation is vastly more common in technical contexts where this scale of measurement appears.