This is the 502nd most frequent Slovenian word.
veliki
"Veliki" in Slovenian means "big" or "large" in English.
The word 'veliki' is used here as an adjective describing the size of the noun 'dog'. In Slovenian, 'veliki' changes form to agree with the masculine singular noun it modifies.
To je veliki pes.
This is a big dog.
In this context, 'veliki' describes the figurative greatness or magnitude of 'achievements'. It's an example of using adjectives for abstract qualities.
Veliki dosežki zahtevajo trud.
Great achievements require effort.
Here, 'Veliki' is a proper adjective as part of a place name and remains capitalized.