Syncytium: Cells, such as heart muscle cells, that are synchronized electrically in an action potential and act as a single cell.

MOOC: An acronym for massive open online course, which refers to Web-based classes designed to make university courses available to a large number of students. MOOCs typically are free and include a series of videotaped lectures by professors, online quizzes and tests, and even community message boards through which students and instructors can interact.

Femtosecond: One-quadrillionth of a second. A femtosecond is to a second what one second is to about 31.7 million years.