key / quay are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
key: (noun) metal device shaped in such a way that when it is inserted into the appropriate lock the lock's mechanism can be rotated. (noun) something crucial for explaining. (noun) pitch of the voice. (noun) any of 24 major or minor diatonic scales that provide the tonal framework for a piece of music. (noun) a kilogram of a narcotic drug. (noun) United States lawyer and poet who wrote a poem after witnessing the British attack on Baltimore during the War of 1812; the poem was later set to music and entitled `The Star-Spangled Banner' (1779-1843). (noun) a coral reef off the southern coast of Florida. (noun) (basketball) a space (including the foul line) in front of the basket at each end of a basketball court; usually painted a different color from the rest of the court. (noun) a list of answers to a test. (noun) a list of words or phrases that explain symbols or abbreviations. (noun) a generic term for any device whose possession entitles the holder to a means of access. (noun) a lever (as in a keyboard) that actuates a mechanism when depressed. (verb) provide with a key. (verb) vandalize a car by scratching the sides with a key. (verb) regulate the musical pitch of. (verb) harmonize with or adjust to.
quay: (noun) wharf usually built parallel to the shoreline.
key: k·IY
quay: k·IY
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)