regarding
v.v. about or concerning a specific subject. You use this word in emails or letters to show what you are writing about.
v. concerning or with respect to a particular subject. Often used in formal or professional correspondence to introduce a topic.
I am writing to you regarding your recent job application.
The manager sent an email to all staff regarding the new office security procedures.
The committee will meet tomorrow to discuss several urgent matters regarding the proposed expansion of the local community centre and its impact on traffic.
By surface analysis, regard + -ing.
Functions as a preposition; typically introduces a noun phrase and does not require 'to' or 'about' after it.
regarding to the matterregarding the matterRegarding is a preposition itself; it should not be followed by 'to'.