The definition for avian is "Relating to birds." Used in a sentence: The old man affectionately referred to pigeons as his "avian friends." The definition for futile is "without purpose, completely ineffective.", the definition for revoke is "To cancel by taking back.", and the definition for trove is "Valuable collection."

The definition for abate is "Become less in amount or intensity." Used in a sentence: Just when it seemed the rain would never stop, the storm suddenly began to abate. The definition for ethical is "conforming to accepted standards.", the definition for opportune is "Suitable or convenient.", and the definition for derivative is "Lacking originality."

The definition for duplicity is "Deceptive thought, speech, or action." Used in a sentence: The life of an undercover detective is filed with necessary duplicity. The definition for moderate is "tending toward the average.", the definition for illuminate is "To make clear.", and the definition for indecorous is "In bad taste."

The definition for periodic is "Occurring at regular intervals." Used in a sentence: The periodic innterruptions of the cuckoo clock prevented Li from concentrating. The definition for lenient is "mild or tolerant.", the definition for clarity is "Clearness.", and the definition for compulsion is "An irresistible impulse."

The definition for retroactive is "effective as of a prior time or condition." Used in a sentence: The retroactive law made even past infractions punishable. The definition for flourish is "to make bold, sweeping gestures.", the definition for combative is "Eager to fight.", and the definition for lenient is "Mild or tolerant."