2. An aid; such as, a word that helps to resolve a situation or a game: The key to solving the crossword puzzle was "siphon".
3. A legend or explanation of markings on a map: Dora checked the key on the street guide so she could determine the distance to the next city.
4. A coral reef off the southern coast of Florida: Have you ever been to the Florida Key?
After studying the key on the map, Bryan traveled to the Florida Key where he located the historic quay.
After Karen's speech, which outlined the key points in the history of the quay, the guide unlocked the gate with her key and the visitors spent the day exploring the quay and admiring the key on the blue sea.