Prefixes and suffixes are two important aspects of many English words given in this pdf file.
A prefix is a letter or group of letters added to the beginning of a word to form a new word, while a suffix is a letter or group of letters added to the end of a word.
Prefixes can change the meaning of a word, and they can also change the grammatical function of a word. For example, the prefix un- can be added to the word happy to form the word unhappy. The prefix dis- can be added to the word agree to form the word disagree.
Suffixes also change the meaning of a word, but they usually don’t change the grammatical function. For example, the suffix -ful can be added to the word hope to form the word hopefully. The suffix -ness can be added to the word sad to form the word sadness.