In recent years there has been an increasing interest on the syntax and interpretation of nominal expressions introduced by ‘unos’ in Spanish. Most of the studies on this topic agree on analyzing this element as a group-marker without clearly expressing the grammatical category to which it belongs. Is ‘unos’ an existential quantifier or is it a determiner? According to Gutiérrez Rodríguez (2005) and Le Bruyn (2010), ‘unos’ can be considered as a determiner, namely, the plural form of the indefinite article ‘un’, with which it shares relevant syntactic and interpretive properties. In addition, regarding its group-marker status, the collective interpretation of ‘unos’ SN is not due to the inherent group value of ‘unos’, given that ‘unos’ SN can also admit distributive reading. So, both readings may depend on some functional properties that merge in the Number portion of nominal expressions.