The income of an individual is generally supposed to be the money returned to him yearly from his investments; the interest return from his stocks, bonds, mortgages, real estate, etc. Of course, the meaning can be extended to include profits from a business, or gains of all kinds, and such is the usual dictionary meaning; but in finance there has been a general tendency to mean only the return from money invested outside of one's direct business, if he has any. The income from a stock arises from profits of the corporation, and is divided among the stockholders in the form of dividends, and may vary from time to time.
The income from bonds and mortgages is generally a fixed amount and is called interest.
1 Edwin A. Howes, Jr., raises this point, which is well to bear in mind: "Income of property consists of the proceeds of what the property produces, the profit which comes from its use in business, or what is paid for its use by another than its owner. Principal, or capital, is the property itself. The absolute owner of the property is likely to treat as income, not only the earnings of the principal property, but all increase which comes from an increase in the value of the property itself, treating as principal what he paid for the property, and as income all excess over the original investment. A person entitled to the use or income of property, or a trustee whose duty it is to pay income to one person or set of persons, hold.