beneficial
The definition for beneficial is "Helpful." Used in a sentence: there is no doubt that eating vegetables is beneficial to one's health.
extenuating
The definition for extenuating is "Partially excusing." Used in a sentence: The extenuating circumstance of Calvin's illness caused the teacher to excuse his lateness.
futile
The definition for futile is "Without purpose, completely ineffective." Used in a sentence: Arguing with Andrew is futile because he never changes his mind.
melodious
The definition for melodious is "Having a pleasing melody." Used in a sentence: The melodious sounds of the symphony soothed Tim after his trying day.
moderate
The definition for moderate is "Tending toward the average." Used in a sentence: The best–selling writer was disappointed; his new novel was only a moderate success.