Col- is a prefix that is commonly used in the English language to describe different things. Some synonyms for the prefix 'col-' are "with", "together", "joint", and "mutual". For instance, the word "collaborate" means to work together. Words such as "collective" and "collimate" are also frequently used to indicate working in unison. In addition, several words start with col-, such as "colleague" which refers to a person working together with someone else, and "collision" which suggests things bumping into one another. Therefore, it is essential to have knowledge of synonyms to make accurate use of the English language.