This is the 1942nd most frequent Arabic word.
والدكتور
"The doctor"
The word "والدكتور" here introduces 'the doctor' as a character performing an action, essentially functioning as the subject of the sentence.
والدكتور في الفصل يشرح الدرس.
And the doctor is in the classroom explaining the lesson.
In this sentence, "والدكتور" identifies a companion accompanying the subject in the action described.
ذهبت إلى المكتبة مع والدكتور.
I went to the library with the doctor.
Here, "والدكتور" serves to indicate one of the interlocutors involved in the discussion, showing its role as a subject in the preposition phrase.