When it comes to academic or training environments, the term "course session" is very common. However, there might be occasions when this phrase sounds too formal or technical. In such cases, it can be useful to have a few relevant synonyms in mind. One option is to use the term "class", which has a more casual tone and could be appropriate for less formal situations. Another possibility is "lecture", a term that emphasizes the educational aspect of the session. "Workshop", "seminar", and "training session" are other alternatives that convey specific types of learning experiences. Finally, "lesson" is a more general term that can be used as a synonym for "course session".