fickle
The definition for fickle is "Lacking constancy, changeable." Used in a sentence: The fickle Senji had a new best friend every month.
incumbent
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.
meticulous
The definition for meticulous is "Extrememly careful regarding details." Used in a sentence: The meticulous detective found every shred of evidence at the crime scene.
pathos
The definition for pathos is "Sympathetic pity." Used in a sentence: The soldiers cherished the kindly Nurse Nightingale for her pathos.
turpitude
The definition for turpitude is "Essential baseness, depravity." Used in a sentence: The turpitude of the villain in the movie offended most audiences.