adjective
Definition: Of crucial importance or significance; something that is essential or necessary.
Example: The key factor in our success was teamwork.
noun
Definition: A small object used to open or close a lock, or a button on a machine that you press to make it work.
Example: I lost my house key and had to call a locksmith.
transitive verb
Definition: To adjust or set something to a specific standard or condition, often in a way that makes it work better or fit together properly.
Example: The technician had to key the settings on the machine to ensure it operated correctly.