"Is this the same shape as before?"

Translation: Ĉu ĉi tio estas la sama formo kiel antaŭe?

[djzeus01]

Still confused about tio vs. tiu...since we're evaluating the shape, aren't we necessarily discussing a specific, known object, and thus require tiu?

[vikungen]

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.

[claire_resurgent]

It is completely normal to use tiu and tia by themselves, without nouns. This course has a hard time conveying that fact of grammar, since English uses "this/that" in almost all cases.

Without a noun::

Use tiu when:

• referring to a person.
• Referring to something concrete that has already been mentioned. This usage is similar to ĝi, but tiu gives the speaker an additional third-person pronoun.
• when the contrast between the thing mentioned and other similar things is topical. "That (one) is very tall (next to the others)." "Tiu estas tre alta."

This sentence is a good demonstration of the kind of differences that aren't usually made in English. "Ĉu tiu ĉi estas sama kiel la antaŭa?" vs "Ĉu tio ĉi estas sama kiel antaŭ?" vs "Ĉu ĝi/tiu estas sama kiel ĝi estas antaŭ?"

• to select something out of a group with tiu el

• When the specific thing mentioned is further identified with a kiu-clause.

Use tia when:

• The nature of a thing, not its individual identity is what is being talked about

• after da

• Making a simile with kia

Use tio when:

• Introducing a new object to conversation and the category of object isn't already obvious.

• Referring to a statement. ("Is that really true?")