Assume there are only 3 people A, B, C working for a company. In other words, the employees of the company consists of A, B and C. So, A is a colleague of B or C.
Machine learning (M) is a field of computer science, consists of supervised learning (S), unsupervised learning (U) and reinforcement learning (R).
Similar to "colleague", is there a term used to describe the relationship between several different and related sub-fields (M, S, U) within a field (R)?
M, S, U and R are not commonly used abbreviation, I used them here just to make the expression easier to understand.