Noun vs Verb

Change the following word to a verb:

invitation

Change the following word to a verb:

apology

Change the following word to a verb:

excuse

Change the following word to a verb:

criticism

Change the following word to a verb:

sympathy

Change the following word to a noun:

compliment

Change the following word to a noun:

complain

Change the following word to a noun:

accept

Change the following word to a noun:

harmonize

Change the following word to a noun:

enter