noun
LEM
noun
1
The Lunar (Excursion) Module, the spacecraft that carried astronauts down to the Moon's surface during the Apollo missions.
"The LEM undocked from the command module and began its descent."
2
Short for the law of excluded middle, the logical principle that a statement must be either true or false, with no third option.
"Some non-classical logics reject LEM entirely."
How to Use LEM
Learner’s notesIn plain EnglishUsually an abbreviation — either for the Apollo Moon-landing craft, or, in logic and philosophy, for the rule that every statement is either true or false.
When to use it
Technical/specialist term in both senses; rarely used outside spaceflight history or logic.
Word Forms
LEMs plural, Lems plural
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The _____ undocked from the command module and began its descent.