The definition for diffident is "Lacking self–confidence." Used in a sentence: The diffident student never raised her hand in class, even when she knew the answer.

The definition for fickle is "Lacking constancy, changeable." Used in a sentence: The fickle Senji had a new best friend every month.

The definition for heinous is "Shockingly evil." Used in a sentence: Eduardo's heinous betrayal of Lydia shocked even Latasha, who knew his evil ways.

The definition for sociable is "Inclined to seek companionship." Used in a sentence: The sociable Glenda was delighted to receive the party invitation.

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.