A couple to share with you today. For US readers, please note that the difference between enquiry/inquiry is general observed more in UK English than US English.
This one is a simple case of noun vs. verb, as follows:
He asked his mother for advice. (noun)
His mother advised him to forget about it. (verb)
Enquire vs. Inquire
These days difference between the two is less observed; however, in UK English it used to be that enquire was used more in the sense of asking about something, whereas inquire had a more formal/investigative sense
He enquired about the book he had ordered.
The inquiry lasted several weeks.
I, personally, observe this one when it's a case of enquiry vs. inquiry, but I always use enquire as the verb.