"That is mainly her work."
Translation:Tio estas ĉefe ŝia verko.
I'm still being confused by tio and tiu. I thought that this sentence indicated that there was a specific something which is supposed to be her work, and that would be tiu. But I was told that tiu is wrong.
Use -u with nouns and -o alone.
Tio estas bela.
Tiu domo estas bela.
Tio estas arboj.
Tiuj arboj estas verdaj.
Per your examples, if the "ti-" word comes directly before a noun it's «tiu», before any other type of word it is «tio». But that would mean «tio estas bela domo» and «tiu domo estas bela.» Which makes no kind of sense to me. In both sentences the ti- word refers to domo. Similarly, in your examples using «arbo» the "ti-" word, again, references «arbo.»
I learned too long ago that «tio» was "that some thing" & «tiu» was "that particular thing". & now I'm reading that I may have to unlearn that for a new mnemonic but no certain mnemonic is being provided.
This hasn't seemed a problem for me until now and that is part of the reason I'm now expressing frustration.
No, in "Tio estas bela domo", the ti- word does not refer to domo - just to "this (thing)". This thing happens to be a house, but the word is not directly referring to it.
In one case, you have a determiner which modifies a noun (tiu domo), in the other case a pronoun which stands by itself (even though it stands for a noun).
So they are two different relations to the noun - a direct description/modification of it and a placeholder for it.
I came here to ask the exact same questions, and while I appreciate the time taken so far to answer, I have to agree that the explanations provided so far have made the ti-u/o question even less clear in my mind.
You might think of it as "Tio estas arbo" is equivalent to "that thing is a tree." That weird blob over there is, in fact, a tree.
Wheras "Tiu arbo estas bela" means "This particular tree is beautiful," and "Tio estas bela arbo" is "That thing over there is a beautiful tree.
Most of the time I still find "that random thing" (tio) and "that specified thing" (tiu) to work best. I still, sometimes, get them wrong, but at least I get them wrong in an explicable manner.
Remember that we are learning from a database, it can only allow for so much flexibility. Real life allows for more, and if you can find some Esperanto literature to read in your off hours then you can find even more examples to apply to your mental database.
Revisiting this question, I think that if I'm familiar enough with a piece of work -- a chunk of code, work of art, piece of writing -- to be able to say to, for instance, Fred, "Ⓣhat is mainly her work," he and I are discussing a specific thing, well-known to us both, which calls for "tiu," and so I've reported this to the developers. See, for instance: http://www.youtube.com/watch?v=0vc-wNwS98o