What is a suffix for begin?

There isn't a single, universally accepted suffix for "begin." However, depending on the context, you could use these options:

To indicate a state of beginning:

* -ing: beginning

* -ment: commencement (formal)

To indicate something that begins:

* -er: beginner (a person)

* -ing: beginning (a noun - the act of starting)

To indicate the result of beginning:

* -er: beginner (a person)

* -er: opener (something that opens)

* -er: starter (something that starts)

The best choice depends on the specific meaning you want to convey.