ansero

One root, and it is worth stopping to say so. Ansero looks as though it might come apart into an- and sero, and a learner who has just met the -an- suffix in klubano and islamano is primed to try. It does not work, for two reasons. There is no root ser- in Esperanto for it to be a member of, and -an- is a suffix rather than a prefix, so it goes after a root and never before one. Anser- is a single Latin word taken in whole.

The genders, and the fact that Esperanto is honest about them. Ansero is the bird in general. Anserino is a female goose specifically, and viransero is a gander, using vir- as the masculine marker rather than any suffix. A gosling is an anserido, built with -id-, the offspring suffix, which is tidier than ansereto because a small goose is not necessarily a young one. The gender article has the whole argument about -in- and vir- and why Esperanto's animal names work this way.

Sitting it beside the neighbours. An anaso is a duck, smaller and shorter in the neck; a cigno is a swan, bigger and white; a kokino is a hen. Ansera means goose-like or silly, which is the same insult English makes of the bird, and anserhaŭto is gooseflesh, built exactly as English builds it.