LEM vs lunar module

LEM and lunar module both are nouns.

Word	Noun	Adjective	Verb	Adverb
LEM	Yes	No	No	No
lunar module	Yes	No	No	No

As nouns, LEM and lunar module are synonyms defined as:

LEM and lunar module: a spacecraft that carries astronauts from the command module to the surface of the moon and back

Other synonyms of LEM include lunar excursion module.

LEM (noun)	lunar module (noun)
a spacecraft that carries astronauts from the command module to the surface of the moon and back	a spacecraft that carries astronauts from the command module to the surface of the moon and back