Breakdown of Он разговаривает с группой туристов.
он
he / it (for a masculine noun) / it (for a neuter noun)
турист
tourist
разговаривать
to talk
с
with (also со)
Questions & Answers about Он разговаривает с группой туристов.
Why does турист change to туристов here?
туристов is the genitive plural form of турист. Because турист is a masculine noun ending in a hard consonant, we add the ending -ов to form the genitive plural. In this sentence, the genitive case is used to mean "of tourists" (a group of tourists).
Since he is talking "with" the tourists, why isn't туристов in the instrumental case?
The preposition с only affects the main noun it connects to, which is группой (with a group). The word туристов depends entirely on the word group, answering the question "a group of what?". Therefore, it takes the genitive case. You are saying "with a group of tourists", not "with a group and with tourists".
Why is the word for group spelled группой?
The preposition с (meaning "with") requires the noun that follows it to be in the instrumental case. The base word is группа (a feminine noun ending in -а), so its instrumental form becomes группой.
Why use разговаривает instead of говорит?
While both mean "to talk" or "to speak," разговаривать specifically means "to converse" or "to have a two-way conversation." Говорить is a bit more general and is often used for one-way speaking, like telling someone a fact or speaking a certain language.