pondering vs brooding

pondering is not a noun while brooding is a noun.

Word	Noun	Adjective	Verb	Adverb
pondering	No	Yes	No	No
brooding	Yes	Yes	No	No

As adjectives, pondering and brooding are synonyms defined as:

Other synonyms of pondering include broody, contemplative, meditative, musing, pensive, reflective, ruminative.

pondering (noun)	brooding (noun)
	persistent morbid meditation on a problem
	sitting on eggs so as to hatch them by the warmth of the body

pondering (adjective)	brooding (adjective)
deeply or seriously thoughtful	deeply or seriously thoughtful