I just completed an excercise by lernu.net. It was about when to use -e and when to use -a. The descprition told me to put an adjective when there was a noun in the phrase, and an adverb when there was none. When I came to this phrase, I disobeyed that pattern:
Tio estas ver_.
I put in Tio estas vere, simply because that sounded more familiar. Now I want to know, is that grammatically wrong? I received no points for this answer.
My question may be extended for more of the correlatives. These are some more phrases where adverbs seem fitting to me:
- Ĉio estas mirinde en nia mondo.
- Io ne estas ĝuste pri ĝi.
But in these cases adjectives are clearly correct:
- Io stranga okazis.
- Mi vidas ĉion helan.