The Latin stem "ad" means "to." In Latin, "ad" is a preposition that is commonly used to indicate movement or direction towards something or someone. It can also be used to express the purpose or goal of an action. For example, in the word "adventures," the prefix "ad-" signifies movement towards or the beginning of something new. Similarly, in words like "adhere" or "admit," the prefix "ad-" implies a sense of going towards or accepting something. Overall, the Latin stem "ad" conveys the idea of "to" or "towards" in various contexts.