'repeat' or 'repetition'

[Sajumon]

How can we make a choice between using 'repeat'(as a noun) and 'repetition'?
Similarly 'invite' and 'invitation'.
Which is correct-I sent him an invite(or invitation) to join an online-quiz programme?

[Haihao]

I would think that 'repetition' can be an instance of repeating while 'repeat' only an act of it.
And "I sent him an invitation to join an online-quiz programme." is, I think, the correct one.

[Cristovam]

Dear Sajumon, one thing is correct: repeat can be verb and noun whereas invite is only verb and invitation only noun. For example: You must repeat that work; this novel should be a repeat; I would like to invite you to a party; I received an invitation to a party. I do not know if I was helpful. Thanks.

[Haihao]

"Invite" can be used as a noun and thus a synonym for "invitation". For example, An invite to an open house Thursday evening at the UN guesthouse.

[Sajumon]

Thank you, Haihao and Cristovam.