"Excuse me, I am a man."
Translation:Pardonon, mi estas viro.
Including the imperative and ‘min’ this early without explaining them first is a bit underhanded.
why is pardonu and not pardonas or pardoni? not sure why and how to use the u in the verbs.
Pardonu is the command form, whereas pardonas is the present tense and pardoni is the infinitive. If you're telling someone to do something (e.g. pardon me), you use the -u.
Are "pardonon" and "pardonu" in this context short for "mi petas pardonon" and "pardonu min" ?
You can use a noun as a verb. Or, more accurately, you can derive a verb based on a root that's a noun (or nominal root for the English majors).
For example, (from the dictionary at http://en.lernu.net/index.php):
broso (bros·o) brush
brosi (bros·i ← bros·o) (tr) to brush