death's head vs symbolization

death's head and symbolization both are nouns.

Word	Noun	Adjective	Verb	Adverb
death's head	Yes	No	No	No
symbolization	Yes	No	No	No

As nouns, symbolization is a hypernym of death's head; that is, symbolization is a word with a broader meaning than death's head:

death's head: a human skull (or a representation of a human skull) used as a symbol of death
symbolization: something visible that by association or convention represents something else that is invisible

Other hypernyms of death's head include symbol, symbolic representation, symbolisation.

death's head (noun)	symbolization (noun)
a human skull (or a representation of a human skull) used as a symbol of death	the practice of investing things with symbolic meaning
	something visible that by association or convention represents something else that is invisible
	the use of symbols to convey meaning