A manufacturing unit containing a number of interconnected cells.

1. The point that is equidistant from all the points on a circle or sphere.

2. The point (if it exists) about which a curve (such as a circle, ellipse, or hyperbola) is symmetrical.

3. The point (if it exists) about which a surface (such as a sphere, ellipsoid, or hyperboloid) is symmetrical.

4. For a regular polygon, the center of its circumscribed circle.

5. The subgroup consisting of all elements that commute with all other elements in a given group.

6. The subring consisting of all elements a such that ax = xa for all x in a given ring.

To adjust the components of an optical system so that their centers of curvature lie on a common optical axis. Also known as square-on.

For a distribution, the expected value of any random variable which has the distribution.