Warren Buffett, who was Graham's best student, has a definition which I agree with. An investor is one who seeks return from the underlying asset itself, whether be earnings/dividends from the underlying company for a stock or rent from a property if it is real estate. A speculator on the other hand seek returns from pure price appreciation. Also in my opinion, an investor sees the stock as a business, while a speculator sees the stock as a ticker symbol. In the mind of an investor, he/she is owner of a sound and profitable business while in the mind of a speculator, he/she is playing a zero sum game trying to beat the other people in the market.