January Barometer: refers to the belief of some traders that the investment performance of the S&P 500 index in January can predict its performance for the rest of the year.

"Jekyll and Hyde": is a literary reference to describe a stock market that seems to have a split personality, mixing good and bad character traits. Jekyll represents the good in a market and Hyde the dangerous for investors.

Jitney: a broker that does not have direct access to a stock exchange and relies on another broker with access to the exchange to execute its trades.

Joint venture (JV): is a business arrangement in which two or more parties agree to pool their resources in order to carry out a specific task. Companies that are in such an agreement are McDonald's (MCD) and Coca Cola (KO).