guideline vs rule of thumb

guideline and rule of thumb both are nouns.

Word	Noun	Adjective	Verb	Adverb
guideline	Yes	No	No	No
rule of thumb	Yes	No	No	No

As nouns, guideline and rule of thumb are synonyms defined as:

guideline and rule of thumb: a rule or principle that provides guidance to appropriate behavior

Other synonyms of guideline include guidepost.

guideline (noun)	rule of thumb (noun)
a rule or principle that provides guidance to appropriate behavior	a rule or principle that provides guidance to appropriate behavior
a detailed plan or explanation to guide you in setting standards or determining a course of action
a light line that is used in lettering to help align the letters