233. In contrast to the pronouns ending in "-u" ("tiu", "kiu", "cxiu",
"iu", "neniu"), a similar series ending in "-o" refers to an object,
fact or action not definitely specified (but never to a person), like
English "what, anything, something, nothing," etc. Because of their
somewhat vague meaning, these pronouns do not occur in the plural, nor
are they ever used as pronominal adjectives:
Demonstrative: tio = that (thing, fact or action).
cxi tio = this (thing, fact or action).
Interrogative and Relative: kio = what.
Distributive: cxio = everything.
cxio cxi = all this.
Indefinite: io = anything, something.
Negative: nenio = nothing.
234. A pronoun (not personal) in predicate or relative relation to a
pronoun ending in "-o" must itself be of the same series:
Kio estas cxi tio, kion vi diras? What is this, which you say?
Sxi vidis tion, kio jxus okazis, she saw that which just occurred.
Cxio cxi, kion vi vidas, estas farita de ili,
everything here (all this), which you see, was done by them.
Li havas ion por vi, sed nenion por mi,
he has something for you, but nothing for me.