Tiu vs. Tio
How do you know when to use "tiu" or "tio"? "Kiu" means who, while "kio" means what, if I understood everything correctly, but then I see sentences like "Tiu objekto estas masxino." An object isn't a who, it's a what. Can somebody explain this please?
1. In combination with a noun, use tiu (never tio), like you'd use an adjective.
-- Tiu libro estas tro multekosta. - That book is too expensive.
2. Use tio by itself.
-- Tio estas mia plej favorata libro. - That is my favourite book.
3. If it's clear from context that you are talking about a particular range of objects, and you wish to pick out one particular specimen from that range, you may use tiu by itself, with the referent strongly implied. This is equivalent to the English that one. For example:
-- Jen la libroj, kiujn mi vendas. - Bone. Kiom kostas tiu [libro]? Here are the books I'm selling. - Great. How much does that one cost?
4. Standalone tiu is the demonstrative equivalent of the terms: "everybody" (ĉiu), "somebody" (iu), "nobody" (neniu). Think of it as meaning "thatbody"! Most anglophones don't have problems with neniu and iu (nobody, somebody). So remember that tiu follows the same pattern - it would be grammatically correct to use it where you'd use the other -u correlatives to refer to people.
-- Mi demandis tion al la politikisto. Tiu [politikisto] donis nur duonrespondon. - I asked the politician that. He ("thatbody") only gave a half-answer.
Years ago, I read an article that offered spoof advice to English-speakers trying to learn French. One of the points was about how to distinguish "de" and "du".
The advice given was: "What difference could it possibly make?"
I have started to feel the same way about "tiu" and "tio". :-)
It’s an interesting point. Here esperanto is more or less willingly introducing an ambiguity —between personality/person/personification (some(one/body), thatbody, no(one/body), every(one/body), each(one/body)) and identification(some, thatone, no, every, each)—, that’s eventually found in other languages, like french (maybe russian too).
That’s typically the kind of semantic ambiguities that occase in languages when, indeed, the semantic difference is generally contextually irrelevant, and that, reducing the range of expressivity, allows to ease the ease of expressivity itself, and make it more natural (contrarily to what people have said of Ido, lojban, etc.).