The prefix "in-" is commonly used in the English language to indicate negation or the opposite of a word. For example, in the word invisible, the prefix suggests that something cannot be seen. It can also imply "not" or "without," as seen in incomplete, meaning not complete. Additionally, "in-" can denote a sense of being inside or within something. For instance, in the word inside, the prefix indicates a location that is within a boundary. This dual function of "in-" makes it a versatile prefix in forming various words.