Questions & Answers about Ο γιατρός ελέγχει τον εγκέφαλο.
Ο is the masculine singular definite article in the nominative case. In this sentence, it means the and goes with γιατρός.
So:
- ο γιατρός = the doctor
Greek articles change form depending on gender, number, and case, so you will not always see the same form for the.
Because τον εγκέφαλο is the direct object of the verb.
Greek shows the job of a noun by using case:
- ο εγκέφαλος = nominative, used for the subject
- τον εγκέφαλο = accusative, used for the direct object
In this sentence, the brain is being checked, so it is the object, not the subject.