The Morpheme
In order to describe the form of the linguistic expressions (phrases, sentences, texts) in a language, we must describe how those complex expressions are built from smaller parts, until ultimately we which the atoms of linguistic form. The term morpheme is used to refer to an atom of linguistic form.
Most languages have a word like the English word 'word', that appears at first to refer to precisely the sorts of minimal linguistic objects we have in mind. But there are two reasons to reject 'word' as the label for the minimal unit of linguistic form:
The term 'word' is ambiguous, referring to at least three different sorts of object.
In many languages, linguistic expressions we would want to identify as words are in fact structurally complex.
We consider the second of these points here; the first is taken up below.
The following are all words of English:
cat cats cat+s catty cat+y help helped help+ed unhelpful un+help+ful bake bakery bak+ery baker bak+er dedicate dedication dedicat+ion rededicate re+dedicate rededicationings re+dedicat+ion+ing+s establish establishment establish+ment antidisestablishmentarianism anti+dis+establish+ment+ari+an+ism
The words in the centre column can be broken down into parts, as indicated in the right-hand column. It is not obvious that those in the left-hand column can be factored in the same way.
A monomorphemic word like 'help' is structurally complex in one sense; it can be decomposed into distinct phonological elements (sounds, if you will), each associated with some configuration of the speech organs. The same is true of 'helped' of course, but that is not what leads up to segment 'helped' into two morphemes: help+ed (/help+t/). The intuition that leads us to divide 'helped' into two parts is that each part is associated with a meaning. Thus, the usual definition of morpheme is something like the following:
A morpheme is the minimal unit of