L vs large integer

L and large integer both are nouns.

Word	Noun	Adjective	Verb	Adverb
L	Yes	No	No	No
large integer	Yes	No	No	No

As nouns, large integer is a hypernym of L; that is, large integer is a word with a broader meaning than L:

L (noun)	large integer (noun)
the 12th letter of the Roman alphabet	an integer equal to or greater than ten
the cardinal number that is the product of ten and five
a cgs unit of illumination equal to the brightness of a perfectly diffusing surface that emits or reflects one lumen per square centimeter