Morphology. Morphemes

There are two groups of words: lexical (or content) and function (or grammatical) words.
Lexical words are called open class words and include nouns, verbs, adjectives and adverbs.
Function words, or closed class words, are conjunctions, prepositions, articles and pronouns.

Affixes are often the bound morpheme. This group includes prefixes, suffixes, infixes, and circumfixes.
There are two categories of affixes: derivational and inflectional.
The other type of bound morphemes are called bound roots. These are morphemes (and not affixes) that must be attached to another morpheme and do not have a meaning of their own.