Selective Service System vs SSS

Selective Service System and SSS both are nouns.

Word	Noun	Adjective	Verb	Adverb
Selective Service System	Yes	No	No	No
SSS	Yes	No	No	No

As nouns, Selective Service System and SSS are synonyms defined as:

Selective Service System and SSS: an independent federal agency that administers compulsory military service

Other synonyms of Selective Service System include Selective Service.

Selective Service System (noun)	SSS (noun)
an independent federal agency that administers compulsory military service	an independent federal agency that administers compulsory military service