Learn Hardcore Russian: Метро в Москве быстрее, чем городской автобус. - The metro in Moscow is faster than the city bus.

"Быстрее" is the comparative form of the adjective быстрый (fast), meaning faster. In this sentence, it indicates that the metro has a higher speed than the city bus. The construction is similar to the English "faster than" where only the quality being compared is put into the comparative form.

What role does чем play in the sentence, and why is there a comma before it?

Чем functions as a conjunction meaning than, introducing the element being compared with the metro—in this case, the city bus. The comma before чем is a standard punctuation rule in Russian that separates the main clause from the comparative clause.

Why is the phrase в Москве written with Москве instead of Москва?

In Russian, when expressing location with the preposition в (in), the noun must be in the prepositional case. Москве is the prepositional form of Москва, so в Москве means in Moscow.

What does the term городской автобус mean, and why is the adjective городской used here?

Городской автобус translates to city bus. The adjective городской (urban or city) is used to specify that the bus in question is a type used for city transport rather than intercity or suburban travel.

What case is the noun phrase городской автобус in, and why is this form used?

The noun phrase городской автобус is in the nominative case. In Russian comparative constructions with чем, the element being compared usually remains in the nominative case because it directly stands as the benchmark against which the first element is measured.

Why is only the adjective describing the metro put into the comparative form, while the adjective городской remains in its basic form?

The sentence specifically compares the speeds of the metro and the city bus. Therefore, only the quality of speed is modified into its comparative form (быстрее). The adjective городской is merely descriptive, identifying the type of bus, and does not require a comparative form since it is not the trait being compared.