What is the root word of "solitary"?

http://www.etymonline.com/index.php?term=solitary

To find the root word of "solitary," we can break it down into its parts. "Solitary" is an adjective that means being alone, isolated, or single. The root word in "solitary" is "solit," which comes from the Latin word "solus," meaning alone or only. The "-ary" suffix is added to form the adjective. By examining the parts of the word, we can determine that the root word of "solitary" is "solit."