The word "decoration" comes from Medieval Latin decoratio (meaning "ornament") and ultimately from Latin decorare ("to adorn, beautify"), derived from decus ("grace, ornament, honor, dignity"), stemming from the Proto-Indo-European root *dek- (to take, accept") with the sense of "adding grace" or "suggesting an idea of accepting or adding something pleasing".  It entered English in the 15th century, initially for cosmetics, then expanding to adornment and honors.  The meaning of "decoration" evolved from covering blemishes (early 15c.) to adorning with something beautiful (1580s).  It is related to "decorate", "décor", and "decorous".

Examples of "decoration" used in a sentence: 
"The only wall decorations are candles and a single mirror." 
"Festive paper decorations had been hung from the ceiling. He was awarded several military decorations." 
"The Roman glass-blowers were masters of all the ordinary methods of manipulation and decoration." 
"Throughout the grand rooms were tasteful decorations on doors and outside, seasonal songs playing."
"The planting of winter and spring-flowering bulbs will supply colorful decoration at a time when most gardens are looking fairly desolate."

Examples of "decorate" used in a sentence: 
"She enjoys decorating the tree at Christmas." 
"Our kids always get so excited when it's time to decorate the Christmas tree."
"The stadium was decorated with several large banners to celebrate the big game." 
"My students helped me decorate the classroom for the Halloween party." 
"We decorated the guest bedroom in shades of white and cream."