What is a group of letters placed at the end of a word to change its meaning?

A suffix is a group of letters added at the end of a word that alters its meaning or grammatical function. For example, adding the suffix "-ing" to the verb "run" changes it to "running," which indicates the present participle form of the verb. Suffixes can also transform a word's part of speech, such as adding "-ness" to "happy," creating the noun "happiness."

In contrast, a prefix, which is another type of affix, is placed at the beginning of a word. A root word serves as the base of a word, to which both prefixes and suffixes can be added. Inflection relates to changes in the form of a word to express different grammatical features, which can involve the use of suffixes but is a broader concept. Hence, the term specifically referring to letters that alter a word's meaning at the end is "suffix."