a. A line serving as a basis, as for measurement, calculation, or location.

b. Something, such as a set of data, used as a basis for comparison or as a control in a study: took x-rays as a baseline for observing later arthritis.

c. A starting point: Interviews with students provided the baseline of our project.

a. The boundary line at either end of a court, as in basketball or tennis.

b. The area near this boundary line: made a basket from the baseline.

c. A style of play in tennis in which the player remains near the baseline and rarely approaches the net.