In the word "toaster" there are two units of meaning: "toast" and "-er." What is the general term, used in descriptive linguistics, for these units of meaning?

Morpheme is the general term that is used in descriptive linguistics, for these units of meaning. A morpheme can be defined as the smallest unit with meaningful idea. Unlike a word, which can stand by its own, a morpheme may or may stand alone depending upon type of morpheme. They are classified into two types;

1. Free Morpheme - they can function independently

2. Bound Morpheme - they are dependent on other words, root, or other bound morphemes and also includes prefixes and suffixes.

For example:

un-trace-able is made up of three morphemes;

un - a bound morpheme meaning 'not'

trace - root, a free morpheme (can function independently)

able - free morpheme meaning 'to do something'

Morphemes are also categorized as either content morphemes or function morphemes.

Function morphemes => prepositions, pronouns, determiners, conjunctions etc.

Content morphemes => nouns, adverbs, adjectives, verbs etc