Types of 'words'
The idea that words are minimal signs does not rest on the claim that the grammatical properties of words are always fully determinate, but merely that they are, crosslinguistically, more determinate than any smaller unit. The words in a periphrastic construction are often grammatically indeterminate in isolation. Yet whereas this indeterminacy is an exceptional property of periphrasis, it is highly typical of subword units. A similar claim applies to morphotactic constancy. Although words may not always be demarcated in the speech stream, they are more clearly and consistently demarcated than any smaller unit.
Some word-based accounts do in fact treat words as unstructured wholes (Singh and Starosta 2003), while others (Anderson 1992; Aronoff 1994; Stump 2001) represent morphological structure more in terms of the ‘derivational history’ defined by spell-out rules than in terms of morphotactic arrangement. Yet even in these accounts the claim that words are grammatically basic remains logically independent of the claim that they exhibit no structure above the phonological level.