The definition for beneficial is "Helpful." Used in a sentence: there is no doubt that eating vegetables is beneficial to one's health.

The definition for deferment is "The act of delaying." Used in a sentence: Sybil was frustrated by the deferment of her much anticipated vacation.

The definition for negate is "To make invalid." Used in a sentence: Paula negated Tiffany's argument by proving that her main premise was false.

The definition for serenity is "Calmness." Used in a sentence: The serenity of the glassy sea soothed the sailors after the big storm.

The definition for stealth is "The act of moving secretly or unnoticed." Used in a sentence: The burglar took the ring by stealth, slipping it from the sleeping woman's finger.