SUPPORT

When referring to the price of an issue over time, support refers to a floor that the price won’t break through. There are several possible reasons that the price won’t fall below this support level. One of the more common reasons is that, at that support price, the number of shares that buyers want to buy exceeds the number of shares that sellers want to sell. Hence, the demand exceeds the supply, so the price will rise to an equilibrium point where trades can take place. When the price won’t rise through a price, that is resistance.

Complete defintion with example graph (in a new browser window).