Do any words have meanings that are predictable – that is, meanings that can be worked out on the basis of the sounds or combinations of sounds that make them up? (I consciously say ‘sounds’ rather than ‘letters’ because writing is secondary to speech: every normal human learns to speak, but it is only in the last century or so that a substantial proportion of the world’s population has learned to read and write.) The answer is certainly ‘yes’, but not necessarily for reasons that immediately come to mind.

It is true that there    are some words whose sound seems to reflect their meaning fairly directly. These include so-called onomatopoeic words, such as words for animal cries: bow-wow, miaow, cheep, cock-a-doodle-doo. But even here convention plays a large part. Onomatopoeic words are not the same in all languages; for example, a cock-crow in German is kikeriki, and a dog’s bark in French is ouah ouah (pronounced roughly ‘wah wah’). There are also sets of words in which some similarity in sound (say, in the cluster of consonants at the beginning) seems to reflect a vague similarity in meaning, such as smoothness or wetness or both in the set of words slip, slop, slurp, slide, slither, sleek, slick, slaver, slug. A technical term for this situation is sound symbolism. But in sound symbolism, quite apart from the role of convention, the sound–meaning relationship is even less direct than in onomatopoeia. The fact that a word begins with sl- does not guarantee that it has anything to do with smoothness or wetness (consider slave, slit, slow), and conversely there are many words that relate to smoothness and wetness but do not begin with sl-.

The idea that some words have meanings that are ‘natural’ or predictable in this way is really a leftover from childhood. Young children who have been exposed to only one language are often perplexed when they encounter a foreign language for the first time. ‘Aren’t cat and dog obviously the right words for those animals?’, an English-speaking child may think; ‘Why, then, do French people insist on calling them chat and chien?’ Pretty soon, of course, everyone comes to realize that, in every language including their own, the associations between most words and their meanings are purely conventional. After all, if that were not so, the vocabularies of languages could not differ as much as they do. Even in onomatopoeia and sound symbolism this conventionality is still at work, so that people who know no English are unlikely to predict the meaning of cock-a-doodle-doo or bow-wow any more accurately than they can predict the meaning of cat or dog.

What kinds of word do have predictable meanings, then? The answer is: any words that are composed of independently identifiable parts, where the meaning of the parts is sufficient to determine the meaning of the whole word. Here is an example. Most readers have probably never encountered the word dioecious (also spelled diecious), a botanical term meaning ‘having male and female flowers on separate plants’. (It contrasts with monoecious, meaning ‘having male and female flowers on the same plant’.) If you had been asked the meaning of the word dioecious before today, you would probably have had to look it up in the dictionary. Consider now sentence (2):

(2) Ginkgo trees reproduce dioeciously.
To work out what this sentence means, do you now need to look up dioeciously in a dictionary? It is, after all, another word that you are encountering here for the first time! Yet, knowing the meaning of dioecious, you will agree (I take it) that a dictionary is unnecessary. You can confidently predict that (2) means ‘Ginkgo trees reproduce by means of male and female flowers on separate plants’. Your confidence is based on the fact that, knowing English, you know that the suffix -ly has a consistent meaning, so that Xly means ‘in an X fashion’, for any adjective X. Perhaps up to now you had not realised that you know this; but that merely reflects the fact that one’s knowledge of one’s native language is implicit, not explicit – at least until aspects of it are made explicit through schooling.

Dioeciously is an example of a word that, although not brand new (it may even be listed in some dictionaries), could just as well be brand new so far. The fact that you could nevertheless understand it (once you had learned the meaning of dioecious, that is) suggests that you should have no difficulty using and understanding many words that really are brand new – words that no one has ever used before. It is easy to show that that is correct. Here are three sentences containing words that, so far as I know, had never been used by anyone before my use of them today, in the year 2000:

(3) Vice-President Gore is likely to use deliberately un-Clintonish electioneering tactics.

(4) It will be interesting to see how quickly President Putin de-Yeltsinises the Russian government.

(5) The current emphasis on rehabilitative goals in judicial punishment may give rise to an antirehabilitationist reaction among people who place more weight on retribution and deterrence.

You will have no difficulty interpreting these sentences. Un-Clintonish tactics are tactics unlike those that President Clinton would use, and a de-Yeltsinised government is one purged of the influence of Boris Yeltsin. The word antirehabilitationist may strike you as ugly or cumber-some, but its meaning is likewise clear. In fact, it is virtually inevitable that words with predictable meanings should exist, given that English vocabulary changes over time. If one examines words that first came into use in the twentieth century, one will certainly encounter some that appear from nowhere, so to speak, with meanings that are unguessable from their shape, such as jazz or gizmo. The vast majority, however, are words whose meanings, if not strictly predictable, are at any rate motivated in the sense that they can be reliably guessed by someone who encounters them for the first time in an appropriate context. Examples are computer or quadraphonic or gentrification, all of which have meanings that are sufficiently unpredictable to require listing in any up-to-date dictionary, but none of which would have been totally opaque to an adult English-speaker encountering them when they were first used.

What these examples show is that one of the characteristics suggested as applicable to all words – that they have meanings that are unpredictable and so must be listed in dictionaries – is not after all totally general. If dioecious and rehabilitation are listed, then dioeciously and antirehabilitationist do not need to be listed as well, at least not if semantic unpredictability is the criterion. And a novel word such as un-Clintonish is perfectly understandable even though the base from which it is formed is a proper name (Clinton) and hence will not be listed in most dictionaries. The link between wordhood, semantic unpredictability and dictionary listing is thus less close than you may at first have thought.

Is it, then, that the common view of words as basic semantic building-blocks of language is simply wrong? That would be too sweeping. What examples such as computer illustrate is that a word’s meaning may be motivated (a computer is certainly used, among other things, for computing, that is for performing calculations) but nevertheless idiosyncratic (it is not the case, in the early twenty-first century, that anyone or anything that performs calculations can be called a computer). In some instances a word’s original motivation is totally obscured by its pronunciation but can still be glimpsed from its spelling, as with cupboard and handkerchief. It is as if words are intrinsically prone to drift semantically, and in particular to acquire meanings that are more specialized than one would predict if one had never encountered them before. Why this should be is a large question, still not fully answered, involving the study of linguistic semantics, of language change, and of how knowledge about words is acquired and stored in the brain. For present purposes, what matters is to be aware that not every word can be listed in a dictionary, even in the fullest dictionary imaginable.