The term "only" refers to something that is unique or singular in a particular context. It emphasizes exclusivity, indicating that there are no others of its kind or that something is the sole example of a category. For instance, if someone says they are the only child in their family, it means they have no siblings. In mathematics, "sole" can refer to a single solution or outcome in a problem. For example, a sole solution to an equation means that there is just one answer that satisfies the conditions of that equation, distinguishing it from cases with multiple or no solutions.