Tertius is a Latin word that means "third" and is often used in medical terminology. Some synonyms for the word tertius include "triassic," "triple," "trinal," "treble," "trine," "thirdly," "third party," and "thirdly speaking." These words all have similar meanings to tertius and can be used interchangeably in many contexts. Additionally, some related terms include "tertiary structure" and "tertiary amino acid," which refer to the three-dimensional arrangement of proteins and the classification of amino acids based on their chemical properties. Overall, tertius and its synonyms are important words in the medical and scientific communities and are used frequently in research and publications.