Source edition 1965. Please read the Introduction
to find out about this dictionary and our plans for it. Caution many entries
have not been updated since the 1965 edition.
Greek symbols may not appear correctly in some browsers. For example
a gamma may appear as γ.
The previous is an excerpt (with the exception of the reference to "ephemeris second") from WWW version of the National Institute of Standards and Technology: Physics Laboratory's International System of Units (SI)
Also, the letters, P, W, Q, R, N, and S are used to designate comparatively rare types of stars which do not fall into the main series.