Ο καθηγητής μιλάει κυρίως ελληνικά στην τάξη.

The professor mostly speaks Greek in class.

Breakdown of Ο καθηγητής μιλάει κυρίως ελληνικά στην τάξη.

• μιλάω: to speak
• ελληνικά: in Greek
• σε: in
• η τάξη: the classroom

Questions & Answers about Ο καθηγητής μιλάει κυρίως ελληνικά στην τάξη.

What does Ο mean here, and why is it Ο and not something else?

Ο is the definite article in Greek, meaning “the” for masculine singular nouns in the nominative case (the basic “dictionary form” of a noun, usually used for the subject).

• Ο καθηγητής = the (male) professor / teacher
• Ο is used because:
  • καθηγητής is masculine
  • It’s singular
  • It’s the subject of the sentence (so nominative case)

Other forms of “the” in Greek are:

• Η (feminine nominative singular) – e.g. η πόρτα (the door)
• Το (neuter nominative singular) – e.g. το βιβλίο (the book)

So we use Ο because καθηγητής is masculine.

What exactly does καθηγητής mean, and how is it different from δάσκαλος?