Derivation is the process of obtaining something from a source or origin. In language, it refers to how new words are formed from existing ones, often by adding prefixes or suffixes. For example, the word happy can become unhappy by adding the prefix "un-," changing its meaning to the opposite. This helps expand vocabulary and allows for more precise expression. In mathematics, derivation involves finding the rate at which a quantity changes. The derivative of a function gives us information about its slope or how steep it is at any point. This concept is crucial in fields like physics and engineering, where understanding change is essential.