kubo

The seam that runs the wrong way. Kubuto, an elbow, arrived earlier in this tier at rank 2627. Meet kubo afterwards and the temptation is obvious: elbow equals cube plus something. It does not. Kubuto comes from Latin cubitum, the elbow and the forearm-length measure that gave English cubit, and kubo comes from Greek kybos, a die. Two roots, two languages, one accidental overlap of three letters.

What makes this one worth flagging is the direction. Most of the false seams in this chapter tempt you to cut a borrowed word into Esperanto pieces. Here the danger is the reverse: you meet the longer word first, on the body vocabulary list, and then the shorter one turns up and looks like the base it was built on. It was not. Nothing in Esperanto is kub- plus -ut-, because -ut- is not a suffix. When two words share a beginning, the test is always whether the remainder is a piece of the language.

The dice came first. A Greek kybos was the thing you threw, and the mathematics borrowed the name of the toy. That history is still visible in the vocabulary of play: ĵetkubo is a die, literally a throw-cube, and ludi per ĵetkuboj is to play dice.

Doing arithmetic in Esperanto. Kubo de tri is the cube of three, kuba the adjective, and kuba metro a cubic metre. The flat relative is kvadrato at rank 2380, the square, and a cube is six squares stuck together - which is what the six equal flankoj of the first example above are.