In this thesis, I investigate the distribution and function(s) of gender in Tunisian Arabic. Based on the observation that gender can ll multiple functions and hence receive different interpretations in TA, I consider gender in this language to be subject to contextual allosemy. Allosemy is the equivalent of conditioned allomorphy at the level of LF (Wood, 2012; Marantz, 2013; Wood and Marantz, 2017) and is de ned as a phenomenon in which a single morpheme can have multiple semantic realizations. My proposal is based on the observation that the interpretation of gender is conditioned by its syntactic environment, more speci fically, by the class of the base noun and the function and interpretation of any node or abstract morpheme (e.g., number) that is parasitic of the n head hosting the class feature. The current predominant view of gender in syntactic theory is that it has a nominalizing function (Lecarme, 2002; Kihm, 2005; Lowenstamm, 2008; Acquaviva, 2009; Kramer, 2009, 2014, 2015; Hammerly, 2018). According to this view, gender is hosted on the n head, which selects the root, and assigns it a nominal category (assuming DM). However, Arabic has other uses for the feminine gender, most of them associated with number. This, I argue, originates from the diachronic trajectory of the feminine a x -a in Proto-Semitic, where it started out as a nominalizer, then a singulative a x, then a group marker, before finally marking feminine gender (Hasselbach, 2014a,b; Dali and Mathieu, 2019a). These subsequent layers of meanings associated with what is now known as gender are all present in the synchronic picture of Arabic. Through an exhaustive inventory of data and diagnostics, I show that the role of gender is pervasive within the Tunisian Arabic DP, and is not limited to nominalization. To account for these facts, I propose that gender is distributed among the different functional heads of the DP: Num, Q, D (see also Farkas 1990; Ritter 1993; Giurgea 2008; Croitor and Giurgea 2009; Steriopolo and Wiltschko 2010; Fassi Fehri 2012, 2018b,a; Dali and Mathieu 2019a). The present thesis also focuses on plurals. I show that plural markers can also be distributed along the nominal spine (Acquaviva, 2008; Harbour, 2008; Wiltschko, 2008, 2012; Butler, 2012; Mathieu, 2012, 2013, 2014; Kramer, 2016), accounting for their di erent functions (e.g., classifying, grouping, counting). These different functions associated with Arabic plurals are, I argue, due to the existence of a singulative operator that is not limited to the collective system, but is pervasive in Tunisian Arabic, as I show. Finally, these observations all suggest that one and the same abstract morpheme (e.g., the feminine and the plural) can receive different interpretations depending on the base they attach to and on their syntactic level, which motivates the allosemic analysis put forward in this thesis.