Directly from "solus":
* Solus: (Formal, literary) alone, by oneself
* Solo: (Music) a piece of music for one performer.
* Solitude: the state of being alone; seclusion.
Words with "sol" as the root:
* Sole: the bottom surface of a shoe or boot.
* Solemn: serious, dignified, and somber.
* Solstice: either of the two times in the year when the sun reaches its highest or lowest point in the sky.
* Solar: relating to the sun.
* Solarium: a room or enclosure exposed to the sun's rays.
Words with "solo" as the root:
* Solo: (Music) a piece of music for one performer.
* Soloist: a performer who plays or sings alone.
Other related words:
* Desolate: barren or deserted.
* Isolate: to separate from others.
* Insulate: to protect from heat, cold, or noise.
* Consolation: comfort received by someone who is feeling sad or disappointed.
These are just a few examples. Many words with "sol" as the root exist in various languages, often related to the sun, isolation, or singularity.