An Etymological Dictionary of Astronomy and Astrophysics
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The change in the shape of a → spectral line over time. For instance, in → Wolf-Rayet stars the line profile varying on time-scales of minutes to hours is attributed to → microturbulence.

→ line; → profile; → variability.

The state of a spectrum from an astronomical object in which the lines change with time as far as their intensity, profile, and wavelength are concerned.

→ spectral; → variability.

The quality, state, or degree of being variable or changeable.

Quality noun from → variable.

A measure of variability of a star (such as Welch-Stetson variability index) which combines the information from two passbands assuming that changes in the star's luminosity occur nearly simultaneously at all optical wavelengths.

→ variability; → index.