what is investment

Just came across words on investment and spend when reading Fisher's book 'The Theory of Interest' -- to spend is to pay money for enjoyment which comes very soon; to invest is to pay money for enjoyment which are deferred in a later time.

Also, another feeling about what income is from the very beginning of the book is the income is a combination of satisfaction from enjoyment from or due to the labor, plus the real money income which can be used to be exchanged with other enjoyment, plus the cost of being alive.