204. The indefinite pronoun iu has a possessive or genitive form ies, somebody's, someone's, a certain one's:
Mi tuŝis ies brakon, I touched someone's arm.
Ĉu ies surtuto kuŝas sur la tablo? Is anybody's overcoat lying on the table?
Ies ludiloj estas rompitaj, someone's playthings are broken.
PARTICIPIAL NOUNS.
205. Nouns may be formed from participles, by substituting the noun ending -o for the adjectival ending -a. Such participial nouns indicate persons temporarily or non-professionally performing or undergoing that which is expressed by the root:
helpanto, one who is helping, an assistant.
elpensinto, one who has thought out something, an inventor.
legonto, one who is about to read.
vidato, one (being) seen.
sendito, one (having been) sent, an envoy.
la juĝoto, the one about to be judged, the accused.
Participial nouns must not be confused with nouns formed by the suffix -ist- (172) expressing professional or permanent occupation: rajdanto, a rider, rajdisto, jockey, horseman, juĝanto, a judge (of something), juĝisto, judge (professional), laboranto, a person working, laboristo, laborer.
THE PREFIX EK-.
206. Sudden or momentary action, or the beginning of an action or state, is indicated by the prefix ek-:
ekdormi, to fall asleep.
ekkanti, to burst into song.
ekiri, to set out, to start.
ekridi, to burst into a laugh
ekrigardi, to glance at.
THE SUFFIX -ID-.