reliquus

Reliquus, reliqua, reliquum, from relinquo: what is left behind. The qu counts as a single consonant, so the word is three syllables, re-li-quus.

Like most quantity words it stands in front of its noun and marks a part rather than the whole: reliqua pars is "the remaining part", not "a remaining part". It works happily as a noun on its own, reliqui for the rest of the people and reliqua for the rest of the things. Two idioms pay for themselves: reliquum est ut with the subjunctive, "it remains to", and nihil reliqui facere, "to leave nothing undone". Ceteri is close but not identical, being all the others of a set already named, while reliqui is what survives after some have gone.