Some lexical words consist of just one morpheme, but many consist of more than one morpheme. Such complex forms are created in one or more of the morphological processes: inflection, derivation and compounding.
You can watch the video version here:
Inflection
Lexical words may be inflected. Inflection is a process in which the identity and class of a word doesn’t change, so the word is still the same lexeme, belonging to the same class. So, a verb is still a verb when inflected, and an adverb is still an adverb.
There are different categories for each word class that are marked by inflection. Here they are along with some examples:
Nouns:
There is the base form like TEACHER, the plural form: TEACHERS and the genitive forms in singular and plural: TEACHER’S and TEACHERS’ respectively.
Verbs:
There is the base form like GET, the third person singular present indicative form: GETS, the past tense form: GOT, the past participle form: GOT / GOTTEN, the present participle form GETTING.
Adjectives:
There is the base form like OLD, the comparative form: OLDER and the superlative form: OLDEST.
Adverbs:
There is the base form like SOON, the comparative form: SOONER and the superlative form: SOONEST.
The genitive form of the noun is a bit problematic, because the genitive suffix is attached to the whole phrase, not just the noun:
the mother of three’s husband
Derivation
The next one of the morphological processes is derivation. This process leads to the creation of new lexemes. The new words either have different meanings or belong to different classes. In the process of derivation new words are created by means of prefixes and suffixes. Here are some examples of words created in the process of derivation, which have different meanings, but belong to the same class:
do – undo (both are verbs, but with opposite meanings)
child – childhood (both are nouns, but with different meanings)
yellow – yellowish (both are adjectives, but with slightly different meanings)
And here are some examples of words which change class, but not the general meaning:
central (adjective) – centralize (verb)
deny (verb) – denial (noun)
fog (noun) – foggy (adjective)
Derivation may be more complex than this. This is the case if more than one prefix and/or suffix is added, like for example in the word COUNTER-PRODUCT-IVE. Or, inflection and derivation may work hand in hand, like in the word DE-CENTRAL-IZE-S, where DE- and -IZE are derivational affixes and –S is an inflectional suffix. In such cases inflectional suffixes always follow derivational suffixes).
Compounding
The last one of the morphological processes is compounding. In the process of compounding new words are created by combining independent bases. There are many options, but the most common ones are:
noun + noun: girl + friend -> girlfriend
verb + noun: guess + work -> guesswork
adjective + noun: black + bird -> blackbird
noun + adjective: sugar + free -> sugar-free
Compounds are usually written as one word or with a hyphen. Their meaning may be predictable from its components, like with SUGAR-FREE, but it may also be unpredictable, like with CHAIRMAN, which is not just a combination of a CHAIR and a MAN, whatever it might be, or BLACKBIRD, which is not just any bird that is black, but a specific species of bird.
There is often a difference in word stress as well. Compare the compound BLACKBIRD and the phrase BLACK BIRD. In the former the first syllable is stressed: BLACKBIRD, whereas in the latter the second word is stressed: BLACK BIRD.
Another difference between compounds and phrases lies in possibilities of substitution. There are none or hardly any in case of compounds, whereas with phrases they are practically unlimited. Here are our two examples again, BLACKBIRD and BLACK BIRD. Let’s try the phrase first. You can substitute either the first or the second word and still obtain something meaningful:
BLACK CAT
BLACK DOOR
BLACK TABLE
or
BLUE BIRD
BIG BIRD
NICE BIRD
But you can’t do it with compounds. Words like *BLACKCAT, *BLACKDOOR, *BLACKTABLE, *BIGBIRD or *NICEBIRD don’t exist. Sometimes substitution is possible, though. BLUEBIRD is an example, it’s another species of bird.