Definition of "key" []

• A notched and grooved, usually metal implement that is turned to open or close a lock. (noun)
• A similar device used for opening or winding: the key of a clock; a can that has a key attached. (noun)
• A means of access, control, or possession. (noun)
• A vital, crucial element. (noun)
• A set of answers to a test. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "_The key to the proper control of China and the building-up of the new Republican State is the railway key_ ...."
• "My eye caught sight of the great key, _Pakenham's key_, lying there on the table."
• "Say that I made bold to assert that you did not possess the key that would unlock the sacred places of her heart; and you may add further, that I say the _key is held by another_."