What do you call a brief, effective saying that conveys a general truth or principle?

The term that refers to a brief, effective saying that conveys a general truth or principle is "aphorism." An aphorism is characterized by its concise and memorable phrasing, often capturing a universal observation or insight into the human experience. These sayings are typically philosophical, social, or moral in nature, making them impactful and thought-provoking.

While the other terms listed have their own meanings, they do not fully encompass the specific qualities associated with an aphorism. For instance, a proverb often carries cultural significance and is typically a traditional saying that expresses a common experience or truth, often rooted in folk wisdom. An adage also conveys a general truth, primarily derived from long-standing wisdom, but it may not be as concise or impactful as an aphorism. Slang, on the other hand, refers to informal language that is often specific to certain social groups or trends, lacking the universal and timeless quality associated with aphorisms. Thus, the unique brevity and depth of meaning found in an aphorism make it the correct choice for this question.