soft soap vs soap

soft soap and soap both are nouns.

Word	Noun	Adjective	Verb	Adverb
soft soap	Yes	No	No	No
soap	Yes	No	Yes	No

As nouns, soap is a hypernym of soft soap; that is, soap is a word with a broader meaning than soft soap:

soft soap: a soft (or liquid) soap made from vegetable oils; used in certain skin diseases
soap: a cleansing agent made from the salts of vegetable or animal fats

soft soap (noun)	soap (noun)
a soft (or liquid) soap made from vegetable oils; used in certain skin diseases	a cleansing agent made from the salts of vegetable or animal fats
flattery designed to gain favor	street names for gamma hydroxybutyrate
	money offered as a bribe

soft soap (verb)	soap (verb)
	rub soap all over, usually with the purpose of cleaning