sharp, sharply

Sharp is usually an adjective.

• Make a sharp right at the gas station.

However, sharp is sometimes used as an adverb meaning “punctually,” “alertly” or “abruptly.”

• Meet me at eight o’clock sharp.
• The captain is coming—look sharp!
• Realizing he had forgotten his bedroll, the cowboy pulled up sharp and rode back to the bunkhouse.

Otherwise, sharply is the standard adverb.

• The commanding officer spoke sharply to her subordinate.