talcum powder vs talcum

talcum powder and talcum both are nouns.

Word	Noun	Adjective	Verb	Adverb
talcum powder	Yes	No	No	No
talcum	Yes	No	No	No

As nouns, talcum powder and talcum are synonyms defined as:

talcum powder and talcum: a toilet powder made of purified talc and usually scented; absorbs excess moisture

talcum powder (noun)	talcum (noun)
a toilet powder made of purified talc and usually scented; absorbs excess moisture	a toilet powder made of purified talc and usually scented; absorbs excess moisture
	a fine grained mineral having a soft soapy feel and consisting of hydrated magnesium silicate; used in a variety of products including talcum powder