Breakdown of Прохожие, идущие по тротуару, просят его выбросить сигарету.
он
he / it (for a masculine noun) / it (for a neuter noun)
идти
to go (on foot) / to proceed, go (of a process)
по
along, around
просить
to ask for, to request
Questions & Answers about Прохожие, идущие по тротуару, просят его выбросить сигарету.
How is the participle идущие formed from the verb идти?
Present active participles are formed from the 'they' form (3rd person plural) of the verb. For идти (to walk), 'they walk' is идут. Drop the -т to get the stem иду-, add the participle suffix -щ-, and finally add the adjective ending. Since it describes the plural nominative noun прохожие, it takes the plural nominative ending -ие, resulting in идущие.
Why are there commas around идущие по тротуару?
In Russian, a participle and its dependent words form a participle clause. If this clause comes right after the noun it describes (here, прохожие), it must be separated by commas. If it came before the noun (Идущие по тротуару прохожие...), no commas would be needed.
Прохожие means "passers-by," but it has an adjective ending. Why?
It is a noun that behaves grammatically like an adjective. These are called substantivized adjectives—words that started out as adjectives but are now used as nouns. You already know words like this, such as столовая (dining room) or мороженое (ice cream).
Why is тротуар (sidewalk) in the dative case here?
The preposition по triggers the dative case when it indicates movement "along", "down", or "across" a surface. Therefore, по тротуару means "along the sidewalk".