Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
regarding, as regards, in regard(s) to, with regard(s) to
In and with regard to, regarding, and as regards are all Standard, synonymous prepositions, slightly longer and more varied than but meaning much the same as about and concerning: I spoke to him regarding [as regards, in regard to, with regard to] his future. With regards to is Nonstandard and frequently functions as a shibboleth, although it can be Standard and idiomatic in complimentary closes to letters: With [my] regards to your family…. In regards to, however, is both Substandard and Vulgar, although it appears unfortunately often in the spoken language of some people who otherwise use Standard. It never appears in Edited English.
1. Wilson is saying that the three phrases: "with regard to", "regarding", and "as regards", are synonyms. He's saying that these three phrases are slightly longer than the two words, "about" and "concerning".
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