cirklo

The fence word arrives. Two hundred ranks ago the cirko page said that cirklo, the geometric circle, sat further down the list "without a page of its own yet" and asked you to keep the two apart in your head anyway. This is that page, and the loop closes here.

Cirklo is a shape. Cirko is a show. They are cousins with the same ancestor and they are not interchangeable in a single sentence. Latin circus was a ring and specifically the oval chariot-racing arena; its diminutive circulus, a little ring, is what Esperanto took for the geometric figure. The adjectives make the split visible at a glance: cirkla is circular, cirka is of the circus. And ĉirkaŭ, the preposition meaning around, is Latin circum from the same family again, which is to say that going round something and running round a racetrack were once one word.

Against rondo, which is the fence that actually costs marks. Rondo at rank 727 covers both the shape and, far more often, a circle of people: a club, a group, a familia rondo. Cirklo is the geometer's word and stays that way. So unu granda rondo familia in La Espero could never be cirklo, and the thing you draw with a compass is never a rondo in a maths lesson. When you mean people, say rondo; when you mean the figure, say cirklo.

The geometry family, now nearly complete.Kvadrato is the square, rektangulo the rectangle, triangulo the triangle, angulo the angle or corner, linio the line and punkto the point. Inside a circle the radiuso is the radius, the diametro the diameter and the cirkonferenco the circumference, all of them borrowed whole and none of them decomposable.

Building on it. Cirkla circular, cirkle in a circle, cirkli to move in a circle, duoncirklo a semicircle. The figurative senses travel too: a vicioza cirklo is a vicious circle, and a cirklo de amikoj is possible but rondo is what a native-sounding Esperantist reaches for.