This is the 2147th most frequent French word.
combien
"How much" or "how many."
Here, 'combien' is used as an adverb to inquire about the quantity or price of something.
Combien ça coûte ?
How much does it cost?
In this sentence, 'combien' introduces a question about the number of students, and it is followed by 'de' before a noun to specify the quantity being asked.
Combien d'élèves sont présents aujourd'hui ?
How many students are present today?
Here, 'combien' is used in a subordinate clause to describe the extent or degree of an action, emphasizing 'how much' he works.