"This wheel works well."
Translation:Tiu ĉi rado funkcias bone.
Why is this "tiu" when the sentence I had just before this one about "Whose pen is that?" had tio, not tiu. Both are indicating a particular object.
I realize this is a year late, but it's the top question and has no answer yet.
Tio replaces a noun and can stand alone. Tiu can not stand alone.
So, in your example, "Kies plumo estas tio?" The "tio" is a noun representing the pen right in front of you.
Tiu is always with a noun. So, "That pen is beautiful" is "Tiu plumo estas bela" because the word "that" isn't a noun and isn't replacing anything.
"Tiu" kaj "tiu ĉi" are not very different. And this is even more confusing for ppl who don't have English as a native language.
It's a matter of proximity. Even if your language doesn't specify this attribute, other languages like Spanish, French, and other languages do.
It makes the difference between this (tiu ĉi) (near to the speaker) and that (tiu) (near to the listener or elsewhere). But if this difference does not matter English speakers tend to say that and Esperanto speakers tend to say tiu.