Allomorph

Allomorph and morphemes

Before we dive straight into allomorphs, let's remind ourselves of what a morpheme is.

A morpheme is the smallest unit of meaning in a language. This means that a morpheme cannot be reduced beyond its current state without losing its basic meaning. This makes it different from a syllable, which is a word unit - morphemes can have any number of syllables.

Morphemes come in two varieties: free morphemes and bound morphemes.

Free morphemes

Free morphemes can stand alone. Most words are free morphemes - some examples include: house, smile, car, peacock, and book. These words carry meaning on their own and are complete in themselves.

Take the word 'tall' for example - it has a meaning on its own and you can't break it down into smaller parts (such as t-all, ta-ll, or tal-l). 'peacock' is also a free morpheme; despite having more than one syllable, it cannot be broken down into smaller parts without losing its basic meaning.

Free morphemes are either lexical or functional.

• Lexical morphemes give us the main meaning of a sentence or text; they include nouns, adjectives and verbs.

• Functional morphemes help to hold the structure of a sentence together; they include prepositions (e.g. with), conjunctions (e.g. and), articles (e.g. the) and pronouns (e.g. her).

Bound morphemes

Bound morphemes cannot stand alone. They have to be bound to another morpheme to carry any meaning. Bound morphemes include prefixes, like -pre, -un, and -dis (e.g. pre-screen, undone, disapprove), and suffixes, like -er, -ing and -est (e.g. smaller, smiling, widest).

Now we have a good idea of what a morpheme is, let's get back to allomorphs.

Allomorph examples

To recap: an allomorph is each alternative form of a morpheme. This could be a variation in sound (pronunciation), or spelling, but never in function or meaning.

Can you spot the allomorphs in the following sentence?

The answer is the indefinite articles 'a', and 'an'. In the sentence above we see both allomorphs: 'an' for when the word following it begins with a vowel, and 'a' for when the word following word starts with a consonant. Each form is spelt and pronounced differently, but the meaning is the same.

Fig. 1 - Allomorphs are like the same morpheme wearing different disguises.

Different types of allomorphs

There is some debate about the different types of allomorphs. For the sake of clarity, we will take you through some examples of the three most common types of allomorphs in the English language: past tense allomorphs, plural allomorphs, and negative allomorphs.

Past tense allomorphs

A past tense allomorph is a linguistic term used to describe different forms of the same morpheme, or grammatical unit, that express the past tense of a verb. In English, we add the morpheme '-ed' to the end of regular verbs to show the action was completed in the past. For example, 'planted', 'washed', and 'fixed'. Other examples of a past tense allomorph include '-d' and '-t' and they are used depending on the sound of the verb in its base form.

'-ed' always has the same function (making a verb past), but is pronounced slightly differently depending on the verb it is bound to. For example, in 'washed' it is pronounced as a /t/ sound (i.e. wash/t/), and in 'planted' it's pronounced as a /ɪd/ sound (i.e. plant /ɪd/).

Try saying these words out loud and you should notice a slight difference in the way the '-ed' morpheme is pronounced.

Struggling to notice the difference? Say these past tense verbs out loud, focusing on the 'ed' morphemes:

• wanted

• rented

• rested

• printed

In each of these words, the 'ed' morpheme is pronounced as /ɪd/.

Now do the same with this set of words:

• touched
• fixed
• pressed

Notice how the 'ed' morpheme is pronounced as /t/.

Each different pronunciation of the 'ed' morpheme is an allomorph, as it varies in sound, but not function.

Plural allomorphs

We typically add 's' or 'es' to nouns to create their plural form. These plural forms always have the same function, but their sound changes depending on the noun.

The plural morpheme has three common allomorphs: /s/, /z/ and /ɪz/. Which one we use depends on the phoneme that precedes it.

When a noun ends in a voiceless consonant (i.e. ch, f, k, p, s, sh, t or th), the plural allomorph is spelt '-s' or '-es', and is pronounced as a /s/ sound. For example, books, chips, and churches.

When a noun ends in a voiced phoneme (i.e. b, d, g, j, l, m, n, ng, r, sz, th, v, w, y, z, and the vowel sounds a, e, i, o, u), the plural form spelling remains '-s' or '-es', but the allomorph sound changes to /z/. For example, bees, zoos, and dogs.

When a noun ends in a sibilant (i.e, s, ss, z), the sound of the allomorph sound becomes /ɪz/. For example, busses, houses, and waltzes.

Other plural allomorphs include the '-en' in words such as oxen, the '-ren' in children, and the '-ae' in words such as formulas and antennae. These are all plural allomorphs as they serve the same function as the more common '-s' and '-es' suffixes.

Negative allomorphs

Think of the prefixes we use to make a negative version of a word, e.g. informal (not formal), impossible (not possible), unbelievable (not believable), and asymmetrical (not symmetrical). The prefixes '-in', '-im', '-un', and '-a' all serve the same function but are spelt differently, therefore, they are allomorphs of the same morpheme.

What is a null allomorph?

A null allomorph (also known as a zero allomorph, zero morph, or zero bound morpheme) has no visual or phonetic form - it is invisible! Some people even refer to null allomorphs as 'ghost morphemes'. You can only tell where a null allomorph is by the context of the word.

Examples of null morphemes appear (or rather, don't appear!) In the plurals for 'sheep', 'fish' and 'deer'. For example, 'There are four sheep in the field'.

We don't say 'sheeps' - the plural morpheme is invisible, and so it is a null allomorph.

Other examples of null morphemes are in the past tense forms of words such as 'cut' and 'hit'.

Fig. 2 - There are four sheep in the yard - but never four sheeps.