reprezentanto

This is a participle wearing a noun ending. Take reprezenti, swap the -i for -ant- and add -o, and you get "the one who is representing". The whole class works this way: parolanto a speaker, komencanto a beginner, loĝanto an inhabitant, vojaĝanto a traveller. There is nothing to memorise, because participial nominals are made on demand from any verb you already know, and the tense travels with them: reprezentinto is the person who used to represent you, reprezentonto the one about to.

Reprezentanto and delegito are not the same job. The difference is baked into the suffixes, and it is a small lesson in reading Esperanto morphology as grammar rather than as vocabulary. -ant- is the ACTIVE participle: a reprezentanto is the one doing the representing. -it- is the PASSIVE one: a delegito is a person who has been delegated, sent by someone else. So a company's agent in another city is a reprezentanto; the person your society picks to attend a congress is a delegito. English blurs the two into "representative" and "delegate" and leaves you to guess which is which.

Watch the accusative. Sendi reprezentanton needs its -n, and so does the plural: ni elektis novajn reprezentantojn. Participial nouns decline exactly like any other -o word - see nouns and adjectives - which is one more thing the affix system gives you for free.