The word "deci" is a prefix that means one-tenth of a unit. It is derived from the Latin word "decimus," which also means "tenth." There are various synonyms for "deci," including "tenths," "tenth parts," or "one-tenth." Another synonym for "deci" is the metric prefix "deka," which means ten times the unit. Similarly, the prefix "centi" means one-hundredth of a unit, while "milli" signifies one-thousandth of a unit. These prefixes are widely used in the metric system and are crucial for measurement and calculation in fields such as science, engineering, and mathematics.