light colonel vs lieutenant colonel

light colonel and lieutenant colonel both are nouns.

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

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

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

light colonel (noun)	lieutenant 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