Fraunhofer lines are absorption lines in the Sun's optical spectrum that were found centuries ago, being the obvious ones. Some are revealed to be multiple lines at current spectral resolutions. Their original Fraunhofer line labels are mostly unused now, but occasionally seen. Each label is a letter, optionally with a subscript, with upper-case an lower-case letters indicating different lines, and upper-case letters A through K being for the prominent lines. Examples:
|D1||589.6||neutral sodium (Na I)|
|E||527.0||neutral iron (Fe I)|
|H||396.8||ionized calcium (CA II)|
A term still seen occasionally is Fraunhofer's G band (or just G band) for the Fraunhofer G line, which was actually multiple lines of nearly the same wavelength in the vicinity of 429.5-431.5 nm.