Questions & Answers about Ο ειδικός περιμένει.
Ο is the masculine singular definite article, so it means the.
In this sentence, Ο matches ειδικός in:
- gender: masculine
- number: singular
- case: nominative
So Ο ειδικός means the expert or the specialist.
ειδικός here means expert or specialist.
It can be:
- an adjective in other contexts, meaning something like specialized
- a noun, as it is here, meaning expert/specialist
So in Ο ειδικός περιμένει, ειδικός is being used as a noun.
Greek uses the definite article very often, including with many nouns referring to people.
So Ο ειδικός is the normal way to say the expert.
If you removed the article and just said Ειδικός περιμένει, it would usually sound less natural in ordinary speech, unless it were a headline, label, or some very special context.