gal vs gallon

gal and gallon both are nouns.

Word	Noun	Adjective	Verb	Adverb
gal	Yes	No	No	No
gallon	Yes	No	No	No

As nouns, gal and gallon are synonyms defined as:

gal and gallon: United States liquid unit equal to 4 quarts or 3.785 liters

gal (noun)	gallon (noun)
alliterative term for girl (or woman)	United States liquid unit equal to 4 quarts or 3.785 liters
United States liquid unit equal to 4 quarts or 3.785 liters	a British imperial capacity measure (liquid or dry) equal to 4 quarts or 4.545 liters
a unit of gravitational acceleration equal to one centimeter per second per second (named after Galileo)