efekto

Two words where English has one, and the fence matters.Efiki at rank 964 is the verb: to have an effect, to work on something, to act. Its noun efiko is the effect in the causal sense - what a medicine does, what a policy achieves, what happens because of a cause. Efekto is the other kind of effect entirely: the impression something makes on an audience. Fireworks have efekto. Aspirin has efiko.

Which means you can say something quite precise, quite briefly. La parolado havis efikon sed neniun efekton - it worked, but nobody was moved. La parolado havis efekton sed neniun efikon - it dazzled, and changed nothing. English needs a sentence for each. This is one of those places where Esperanto's habit of importing a root twice, from different European traditions, has left it with a distinction worth keeping rather than a redundancy worth tidying.

Stage and screen. The theatrical use is the commonest: scenefektoj, lumefektoj, sonefektoj, and specialaj efektoj for what a film does with a budget. Fari efekton is to make an impression; por la efekto is for show. The adjective efekta means showy or designed to impress, and it is quietly critical - the English cousin is theatrical said about a person.

The neighbours. Impreso is the impression from the receiving end, what you were left with. Rezulto is the outcome, neutral and countable. Influi is to shape something over time. And efika as an adjective means effective, not impressive, which is the mistake English speakers make on their first day with this pair.