flybridge vs bridge deck

flybridge and bridge deck both are nouns.

Word	Noun	Adjective	Verb	Adverb
flybridge	Yes	No	No	No
bridge deck	Yes	No	No	No

As nouns, bridge deck is a hypernym of flybridge; that is, bridge deck is a word with a broader meaning than flybridge:

flybridge: the highest navigational bridge on a ship; a small (often open) deck above the pilot house
bridge deck: an upper deck where a ship is steered and the captain stands

Other hypernyms of flybridge include bridge.

flybridge (noun)	bridge deck (noun)
the highest navigational bridge on a ship; a small (often open) deck above the pilot house	an upper deck where a ship is steered and the captain stands