"They are old."
yes, the difference is the inclusion of the noun "zvířata".
- To jsou stará zvířata.
- To jsou zvířata.
- To nejsou zvířata.
- Jsou to zvířata.
- Nejsou to zvířata.
are all ok, but
- To jsou stará.
is not. the only related sentence with a nounless adjective used predicatively that works would be
- To je staré.
i note that in that case the natural gender of "to" (singular neuter) matches that of the adjective, so in that last sentence we are really dealing with a slightly different "to".
an exceptional, very informal/expressive sentence that also works is
- To je stará.
where "stará" is not an adjective despite the appearances, but instead functions as a noun meaning the speaker's wife or girlfriend.
I was thinking it was the absence of the noun, but other places we were discussing how je to/to je and jsou to/to jsou were interchangeable. that may have been not referring to a sentence without a noun. I will have to review with that in mind, or look for a reply here. thanks for the answer you gave, too.
I'm having difficulty knowing when to use the pronoun (oni in this case) and when not. In some cases it doesn't seem to matter, using or not using appears interchangeable... But in other cases without pronoun it is talking generally about all the old people in the world, vs. These specific people being old.
Sorry for my confusion, thanks if you can give me some insight. So far I've learned a lot by asking questions!
The Tips contain this:
- Animate masculine nouns ending in a consonant in the singular usually append -i to form the plural, e.g., muž becomes muži (men) and kluk becomes kluci (boys). Note the consonant shift from k to c before the -i.
- The consonant shift from k to c also impacts the animate masculine hard adjective before the -í ending. Thus we get from velký kluk (big boy) to velcí kluci (big boys).
This is true for other hard consonants as well and the consonants they are paired to were mentioned elsewhere (h -> z, ch -> š, k -> c, r -> ř, d -> ď, t -> ť, n -> ň). Don't forget the softening effect of I and Í on the preceding D T and N in Czech orthography.