Natural languages come in two different modalities – the aural-auditory modality of spoken languages and the visual-gestural modality of sign languages. The impact of modality on the grammatical system has been discussed at great length in the last 20 years. By contrast, the impact of modality on semantics in general and on ambiguities in particular has not yet been addressed in detail. In this paper, we deal with different types of ambiguities in sign languages. We discuss typical lexical and structural ambiguities as well as modality-specific aspects such as ambiguities in the use of the signing space and non-manual markers. In addition, we address the questions how sign languages avoid ambiguities and to what extent certain kinds of ambiguities and non-ambiguities depend on the visual-manual modality of sign languages. Since gestures use the same articulatory channel that is also active in the production of signs, we also discuss ambiguities between gestures on the one hand and grammaticalized gestures and signs on the other.

This research was partly made possible by a grant awarded by the Spanish Ministry of Economy and Competitiveness (FFI2012-36238), by the Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya (2009SGR00763), by SignGram Cost Action IS1006 and by the Courant Research Center ‘Textstructures’ at the University of Göttingen.