The definition for extol is "To praise highly." Used in a sentence: The statesman extolled the ambassador who single–handedly negotiated the peace treaty.

The definition for impenitent is "Lacking remorse." Used in a sentence: The impenitent criminal received a harsh penalty, but his remorseful accomplice was released.

The definition for incumbent is "Necessary as a duty or responsibility." Used in a sentence: It was incumbent on Jack to attend his father's retirement party.

The definition for mandate is "An official order or commission to do something." Used in a sentence: Martha reluctantly obeyed the mandate to vacate her apartment.

The definition for periodic is "Occurring at regular intervals." Used in a sentence: The periodic innterruptions of the cuckoo clock prevented Li from concentrating.