Decamillionaire

Decamillionaire is a term used for someone with a net worth of over 10 million of a given currency, most often U.S. dollars, euros or pounds sterling. The term decamillionaire is made up of two words, “deca” and “millionaire.” The word “deca” or “deka” is of Greek origin, meaning ten. The International System of Units (SI) also defines the prefix “deca” as ten. While the word millionaire is used for someone whose net worth or wealth is equal to or more than a million (1,000,000). When we combine these two to reflect the wealth of a person, it becomes ‘ten times a million,’ which mathematically works out as: 10 x 1,000,000 = 10,000,000. The term is most often used as a benchmark for wealth in countries with currencies that compare to the value of the U.S. dollar, euro or British pound sterling.

A person who has 2.5 million in a given currency can be called a multimillionaire and so can somebody who has 10 million. While the first one has ‘2.5 times a million,’ the second one has ’10 times a million,’ which is a sizable difference not well represented by the traditional net-worth categorizations. Thus, the term decamillionaire is used to reflect the size of one's wealth more precisely. 

Often, wealthy individuals are clubbed together in the category of ‘millionaires’ or ‘multimillionaires,’ but this segregation is too broad to accurately describe a person's wealth. Some wealth management firms further categorize wealthy individuals or families as "high-net-worth," "very-high-net-worth" or "ultra-high-net-worth."

For the sake of simplicity, U.S. dollars will be used to provide a guide to how much wealth qualifies an individual for each of these categories. A high-net-worth individual is one with at least $1 million in investable assets (such as equities and bonds) excluding their primary residence. Different banks or wealth management firms may have their own definitions or thresholds, however. A very-high net worth individual is one with at least $5 million in investable assets, sometimes referred to as a "pentamillionaire." Meanwhile, an ultra-high-net-worth individual is one with at least $30 million to invest. As of 2016, there were just over 73,000 ultra-high-net-worth individuals in the United States.

Given how broad these definitions are, terms like decamillionaire are used to provide a more accurate snapshot of individual wealth. With the ever-increasing number of millionaires the world over, and with the effect of inflation on buying power of their wealth, terms like decamillionaire are used to delineate simple millionaires from those with multiple times the amount of wealth.