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.
  • The description as you report it is too imprecise. It does not matter whether there is a noun in the phrase or not, but what the vere_/_vera refers to. Tio itself is not a noun, but it acts as a nominal element (as evidenced by the -o ending), so if you want to refer to it, use the adjective. If you refer to the verb (estas), use an adverb, regardless of whether there is a noun around or not. Commented Nov 25, 2016 at 9:03
  • I'll reread it and check that I fairly represented it. Commented Nov 25, 2016 at 16:48

3 Answers 3


The -o correlatives are noun-like and although they don't take a plural, they are described by adjectives, not adverbs. Therefore, in every case that you listed, you would need an adjective.

  • Tio estas vera.
  • Ĉio estas mirinda en nia mondo.
  • Io ne estas ĝusta pri ĝi.

Your last two examples could be adverbs depending on what you mean.

  • Io stranga okazis - something strange happened.
  • Io strange okazis - something happened strangely.

I'm not sure what this one means.

  • Mi vidas ĉion helan.

In any of the cases above, changing the adjective to an adverb means that you're describing the verb, not the -o correlative.

  • Clear! Thank you. The last one, yes... I was trying to think of a good example using the accusative. I thought this one meant the same as "Mi vidas cxion kio estas hela" Commented Nov 24, 2016 at 20:29
  • In that case, I that sentence sounds good to me "Mi vidas cxion helan" - I see all the bright things. Commented Nov 25, 2016 at 1:38

put in Tio estas vere, simply because that sounded more familiar. Now I want to know, is that grammatically wrong?

Yes. It is wrong. Tio takes the place of a noun. Describing a noun with an adverb doesn't work. Adverbs modify verbs (they also modify adjectives and other adverbs).

Tio estas vere = That thing (tio) really is (estas vere)... - It is an incomplete sentence. That thing really is what? Also in this case, it is better form to say vere estas rather than estas vere.

When you say Tio estas vera, it means that thing (tio) equals (estas) true (vera).

There are 70 hits in the tekstaro for Tio estas vera. There are a few hits for Tio estas vere but only when there is an accompanying adjective.

  • Good answer. Though just two small details… Adverbs may modify adjectives or other adverbs, not just verbs. The sentence Tio estas vere, although very unusual, is actually grammatical correct, because one can use the existential meaning of esti (as in: Mi pensas, do mi estas. = I think, therefore I am.; Estu lumo! = Let there be light!). Commented Nov 27, 2016 at 19:29

With an -e, the word is an adverb and modifies the verb (or adjective). So tio estas vere is translated as that truly is.

An adverb answers the question how?.

If you want to modify the subject of the sentence you need to use an adjective.

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