This is the 495th most frequent Greek word.
αστυνομικούς
"Αστυνομικούς" means "policemen" or "police officers" in English.
Here, 'αστυνομικούς' is in accusative plural, used as the direct object of the verb 'είδα' (I saw).
Είδα δύο αστυνομικούς να περπατούν στον δρόμο.
I saw two police officers walking on the street.
In this context, 'τους αστυνομικούς' is in accusative plural, again after the preposition 'με' (with), referring to multiple police officers.
Ο οδηγός μίλησε με τους αστυνομικούς αφού τον σταμάτησαν στον δρόμο.
The driver talked with the police officers after they stopped him on the road.
In this sentence, 'αστυνομικούς' is in accusative plural, used as the object of the preposition 'με' (with), while 'Οι αστυνομικοί' is nominative plural, the subject of the sentence.