futo

The fence: futo is the measurement, piedo is the body part. English uses one word for both and Esperanto refuses to, which is the whole reason this page exists. You stand on your piedoj; a ceiling is naŭ futojn alta. Never say tri piedoj for three feet of length - it means three actual feet, which is one more than most readers have.

It was never one length. The Reta Vortaro defines futo as a unit "roughly the size of a foot, varying between countries from 26.5 to 33 centimetres", and that is the honest description of it before the international foot was fixed at 30.48 cm in 1959. A Rhineland foot and an English foot were different objects with the same name, which is a good part of why the metric system won.

Esperanto is a metric language, and says so. Zamenhof's own texts and essentially all modern usage measure in metroj and centimetroj. Futo earns its place for two jobs: translating from English, and reading the older literature. The same goes for colo (an inch), jardo (a yard) and mejlo (a mile) - imported units, kept for the texts that need them.

Grammar note on the examples. "Ten feet wide" puts the measurement in the accusative: dek futojn larĝa. Esperanto uses the accusative for extent of measure exactly as it uses it for extent of time (li restis tri tagojn), and no preposition is needed.