Breakdown of У меня есть билет, и я приглашаю друга на концерт.
и
and
я
I
друг
friend
на
on, at / by (transport) / to (a place) / to (in answer to)
Questions & Answers about У меня есть билет, и я приглашаю друга на концерт.
Why is the word for friend spelled друга here instead of друг?
Because it is the direct object of the verb приглашаю (I am inviting), it needs the Accusative case. As this lesson teaches, for animate masculine nouns (like people and animals), the Accusative form takes the exact same ending as the Genitive case, which means adding an -а to the end.
Why didn't the endings change for билет (ticket) or концерт (concert)?
Билет is actually the subject in the phrase У меня есть билет (literally "By me is a ticket"), so it remains in the basic Nominative case. The word концерт is in the Accusative case because it follows the preposition на (to), but since it is an inanimate masculine noun (a thing, not a living being), its Accusative form looks exactly like its dictionary form.
Why do we use the preposition на for "to the concert" instead of в?
For public events, activities, and open spaces (like a concert, a meeting, or work), Russian uses the preposition на instead of в. Because you are talking about motion toward this event, you use на followed by the Accusative case (на концерт).
Why does the sentence say У меня есть билет instead of using a verb for "I have"?