To define communication and language, we frequently assume that verbal communication is carried by sound, and that gestures only carry non-verbal communication. But verbal communication can also be expressed through the gestural medium. In this presentation, through the study of sign languages, I will explain which kind of difference we can make about verbal / non-verbal an spoken / gestural terms. Some specificities of sign languages lie in the simultaneity of information, the iconicity included in the lexicon or the use of a three-dimensional space to articulate syntactic structures. Another particularity of sign languages is the bimodal bilingualism that signers experience. Native exposure to sign language is far from the most common situation, and the majority of deaf people acquire sign language more or less later in life (school, university, friends, etc.). Therefore, sign languages are used by signers with a wide variety of socio-cultural and language profiles. Language skills of deaf signers can be situated on a continuum ranging from an efficient bimodal bilingualism - sign language and spoken language in its oral and/or written form - to a total absence of speech language mastery whether sign, spoken or written (Estève, 2011; Mugnier, 2006 ; Quinto-Pozos et al., 2017a). In this presentation, I will expose the bimodal consequences on sign language structure and sign language skills.