lunar module vs LEM

lunar module and LEM both are nouns.

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

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

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

Other synonyms of lunar module include lunar excursion module.

lunar module (noun)	LEM (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