demeanor
The definition for demeanor is "Behavior towards others." Used in a sentence: Carlos was well liked because of his charming demeanor.
fickle
The definition for fickle is "Lacking constancy, changeable." Used in a sentence: The fickle Senji had a new best friend every month.
incongruous
The definition for incongruous is "Not harmonious, incompatible." Used in a sentence: Sadie's cowboy hat was incongruous with her black cocktail dress.
serenity
The definition for serenity is "Calmness." Used in a sentence: The serenity of the glassy sea soothed the sailors after the big storm.
straddle
The definition for straddle is "To favor opposing sides." Used in a sentence: Kia straddled the issue, not wanting to say whether James or Tara was right.