key

"She handed me the key to her apartment."

"He lost his car key while walking in the park."

"The old key was rusty but still worked perfectly."

"Please key in your password to access the system."

"He carefully keyed the data into the computer."

"Make sure to key the code correctly for it to work."

"Communication is key in any successful relationship."

"This meeting is a key opportunity to discuss our plans."

"Understanding the market is key to our business success."