chicken vs yellow-bellied

chicken is a noun but yellow-bellied is not a noun.

Word	Noun	Adjective	Verb	Adverb
chicken	Yes	Yes	No	No
yellow-bellied	No	Yes	No	No

As adjectives, chicken and yellow-bellied are synonyms defined as:

Other synonyms of chicken include chickenhearted, lily-livered, white-livered, yellow.

chicken (noun)	yellow-bellied (noun)
a domestic fowl bred for flesh or eggs; believed to have been developed from the red jungle fowl
a foolhardy competition; a dangerous activity that is continued until one competitor becomes afraid and stops
the flesh of a chicken used for food
a person who lacks confidence, is irresolute and wishy-washy

chicken (adjective)	yellow-bellied (adjective)
easily frightened	easily frightened