lieutenant colonel vs light colonel

lieutenant colonel and light colonel both are nouns.

Word	Noun	Adjective	Verb	Adverb
lieutenant colonel	Yes	No	No	No
light colonel	Yes	No	No	No

As nouns, lieutenant colonel and light colonel are synonyms defined as:

lieutenant colonel and light colonel: a commissioned officer in the United States Army or Air Force or Marines holding a rank above major and below colonel

lieutenant colonel (noun)	light colonel (noun)
a commissioned officer in the United States Army or Air Force or Marines holding a rank above major and below colonel	a commissioned officer in the United States Army or Air Force or Marines holding a rank above major and below colonel