The best replacement for invitation is invite.

The best alternatives to invitation are rated as following:
★★★★★  invite
★★★  announcement
★★  christening
★  announcements
★  save the date

Your alternative for invitation is not listed? Suggest!
Speaking about invitation, one probably shouldn't forget about rsvp.

Other search terms related to invitation and their ratings are:
★★★★★ rsvp
★★ inner envelope
★★ wording
★ reply card
recipe card
You have in mind a companion for invitation and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of invitation in all years. Click on graph for more.
invitation
invite
announcement