1. A distinctive feature of a set, object, or attribute. Characteristics of a set are its name and type; of an object is its name; of an attribute are its label, count, representation code, units, and value. See also character. 2. The integer part of a common logarithm. 3. The exponent number for a quantity expressed in scientific notation. 4. As an adjective or prefix, often written in the German, eigen, as in eigencurrent, eigenfrequency, eigenfunction, eigenstate, eigenvalue, eigenvector (see individual entries).