The unit of meaning above a morpheme is a word, although many morphemes, such as walk, can be words all on their own. It’s rather difficult to say what a word is. Some will say that a word can exist only if it is found in a dictionary. Others will say that even then it may not be a word. Equally, we may come across a word that is so new that it may not yet have found its way into any dictionary.
In ‘The Cambridge Encylopedia of the English Language’, David Crystal defines ‘word’ as
the smallest unit of grammar that can stand alone as a complete utterance, separated by spaces in written language and potentially by pauses in speech.
In ‘Language and Linguistics: The Key Concepts’, another linguist, R L Trask, says it is
a linguistic unit typically larger than a morpheme but smaller than a phrase
These definitions are helpful, because they emphasize the grammatical significance of a word and don’t get us bogged down in the question of whether or not a word has to convey meaning. Lewis Carroll’s verse ‘Jaberwocky’ shows how we can identify the role a word is playing in a sentence without our having a precise idea of what it means. It begins, you may remember,
Twas brillig and the slithy toves
Did gyre and gimble in the wabe.
Brillig, slithy, toves, gimble and wabe are all words invented by Lewis Carroll, but if we can recognise brillig and slithy as adjectives, toves and wabe as nouns, and gimble as a verb, doesn’t that make them words? If they aren’t words, then what are they?
Whatever general definition of a word we may agree on, there remain difficulties. Are house and houses one word or two? How about do and does? Same word or different words? Part of the answer is that you wouldn’t expect to find houses or does as the main entries in a dictionary. What you’d look for would be house and do. Fortunately, there are labels to help us get around this kind of difficulty. The word as it occurs in a text, or the word that a word processing program counts, is called an orthographic word (or a token). The word you look up in a dictionary is a lexeme (also known as a lemma).