Questions & Answers about Evenemanget börjar klockan tio.
Because -et is the definite article attached to the noun.
- evenemang = an event
- evenemanget = the event
In Swedish, the definite article is usually added to the end of the noun instead of being a separate word like the in English.
Since evenemang is a neuter noun (ett evenemang), its singular definite form is evenemanget.
Börjar is the present tense form of the verb börja.
- att börja = to begin / to start
- börjar = begins / is beginning / starts
Swedish verbs are simpler than English verbs because they do not change for different persons:
- jag börjar = I begin
- du börjar = you begin
- han/hon börjar = he/she begins
- vi börjar = we begin
So börjar is the correct form here because the sentence is saying what happens now or in the future as a scheduled event.