hierarchical data structure vs hierarchical structure

hierarchical data structure and hierarchical structure both are nouns.

Word	Noun	Adjective	Verb	Adverb
hierarchical data structure	Yes	No	No	No
hierarchical structure	Yes	No	No	No

As nouns, hierarchical data structure and hierarchical structure are synonyms defined as:

hierarchical data structure and hierarchical structure: a structure of data having several levels arranged in a treelike structure

hierarchical data structure (noun)	hierarchical structure (noun)
a structure of data having several levels arranged in a treelike structure	a structure of data having several levels arranged in a treelike structure