An Etymological Dictionary of Astronomy and Astrophysics

1. The state of being likely or probable; a probability or chance of something.
   
2. In technical language likelihood is not synonymous for probability. Same as → likelihood function.

Etymology (EN): From → likely + -hood a suffix denoting state, condition, character, nature, etc., from M.E. -hode, -hod, O.E. -hād (cf. Ger. -heit).

Etymology (PE): Šodvâri, noun of šodvâr, → likely.