Sol is the name or personification of the Sun, as originally used in Latin.
The name is widely known, but not common in general English usage, although the related adjective solar is. It seems to be more frequently used in science fiction writing as a formal name for the star, perhaps to avoid the geocentric associations of the word Sun. By extension, the planetary system orbiting is often referred to as the "Sol System."
A sol is a colloidal solution in which the system is apparently liquid. If water is the continuous phase, the system is called a hydrosol. The term sol is also applied to the dispersion medium of a colloidal solution. See sol (colloid) for more details.