s.t.p. vs standard pressure

s.t.p. and standard pressure both are nouns.

Word	Noun	Adjective	Verb	Adverb
s.t.p.	Yes	No	No	No
standard pressure	Yes	No	No	No

As nouns, standard pressure is a hypernym of s.t.p.; that is, standard pressure is a word with a broader meaning than s.t.p.:

s.t.p.: standard temperature and pressure
standard pressure: a unit of pressure: the pressure that will support a column of mercury 760 mm high at sea level and 0 degrees centigrade

Other hypernyms of s.t.p. include atm, atmosphere, standard atmosphere, standard temperature.

s.t.p. (noun)	standard pressure (noun)
standard temperature and pressure	a unit of pressure: the pressure that will support a column of mercury 760 mm high at sea level and 0 degrees centigrade