Breakdown of Во вторник мои друзья едут в город.
друг
friend
город
city
мой
my (мой, моя, моё) / mine
ехать
to go (by vehicle)
Questions & Answers about Во вторник мои друзья едут в город.
Why is it Во вторник instead of В вторник?
The word вторник starts with two consonants (вт-). Because the very first letter is a в, saying в вторник would be almost impossible to pronounce clearly. To fix this, Russian adds an о to the preposition, making it во вторник.
The lesson says days of the week use the Accusative case. Why does вторник look like its normal dictionary form here?
You are right that it is in the Accusative case! When we say "on a day" (like "on Tuesday"), we use в (or во) + Accusative. However, вторник is a masculine "inanimate" (non-living) noun. Masculine inanimate nouns don't change their endings in the Accusative case, so it looks exactly the same as the basic dictionary form.
Why does this sentence use едут for "are traveling"?
Едут is the "they" form of ехать, which means to go or travel by vehicle. Since they are going to the city, the sentence implies they are taking a car, bus, or train. If they were just walking on foot, you would use идут instead.
What is the singular form of друзья?