At the very core of language is the word – the free-standing unit that unifies form and meaning. The word lists or lexicons of languages hold a vast number of words – an estimated 32,000 for adult speakers of English, for example. Many words are complex, consisting of more than one component that bears meaning and/or plays a grammatical role. The study of these complex word forms is the domain of morphology and the subject of this unit. In it, we will show that sign languages have a wide range of morphological processes, some fully productive, some idiosyncratic, all influenced by general linguistic organizing principles and most molded by modality-specific factors as well. In a sense that will become clear in the following sections, a lot of the “action” in sign language grammar takes place in the morphology.

Three observations suggest why sign language morphology may give us so much insight into the workings of the grammatical system. First, all natural sign languages have an iconic base. Indeed, it would be quite odd for a language in a manual–visual modality to avoid exploiting its ability to represent visual images and spatial relations iconically. Yet, despite the fact that they are often based on iconic images, the words of sign languages may be morphologically complex. In fact, the second noteworthy point is that there are many processes for making complex words in these languages. In some of these processes, the component parts of complex words are also relatively transparent.