Joists are small wall-to-wall metal beams or horizontal timbers that support floors and ceilings. These joists may be made of concrete, wood or steel and are often supported by beams. Found on http://www.designbuild-network.com/glossary/joists.html
A framing member, often a 2' x 10' piece of lumber, which is usually spaced every 16' to 24' and supports the sub-floor and flooring. The joist usually 'sits' on a load bearing wall or beam. Found on http://www.soundhome.com/glossary