Unless you are following a style guide that specifies otherwise, observe the following conventions.
Use acronyms to shorten phrases in order to save space or to avoid awkward repetition of phrases. Acronyms are abbreviations of the things they represent and are formed by combining the first, and sometimes other, letters of the principal words.
AIDS Acquired Immunodeficiency Syndrome RAM random-access memory ROM read-only memory DOS Disk Operating System FTP file transfer protocol HTML Hypertext Markup Language HIV Human Immunodeficiency Virus
Hypertext Markup Language (HTML) was never intended to be a common programming language. The original assumption was that most word processing applications would automatically generate HTML code.
This convention is necessary to avoid ambiguity. NMR, for example, may refer to nuclear magnetic resonance or to the National Maritime Repository.
The number of MDs in the region has declined.