giant sequoia vs Sequoiadendron giganteum

giant sequoia and Sequoiadendron giganteum both are nouns.

Word	Noun	Adjective	Verb	Adverb
giant sequoia	Yes	No	No	No
Sequoiadendron giganteum	Yes	No	No	No

As nouns, giant sequoia and Sequoiadendron giganteum are synonyms defined as:

giant sequoia and Sequoiadendron giganteum: extremely lofty evergreen of southern end of western foothills of Sierra Nevada in California; largest living organism

Other synonyms of giant sequoia include big tree, Sequoia gigantea, Sequoia Wellingtonia, Sierra redwood.

giant sequoia (noun)	Sequoiadendron giganteum (noun)
extremely lofty evergreen of southern end of western foothills of Sierra Nevada in California; largest living organism	extremely lofty evergreen of southern end of western foothills of Sierra Nevada in California; largest living organism