beneficial
The definition for beneficial is "Helpful." Used in a sentence: there is no doubt that eating vegetables is beneficial to one's health.
fickle
The definition for fickle is "Lacking constancy, changeable." Used in a sentence: The fickle Senji had a new best friend every month.
heed
The definition for heed is "To pay attention to." Used in a sentence: "Heed my advice," the fortuneteller warned Sebastian when he tried to ignore her prophecy.
supple
The definition for supple is "Flexible." Used in a sentence: The supple leather coat draped like soft cloth around her shoulders.
turmoil
The definition for turmoil is "Extreme confusion, agitation." Used in a sentence: The windstorm caused such turmoil in the lake that the sailboat capsized.