Human languages, signed and spoken, can be characterized by the structural patterns they use to associate communicative "forms" with "meanings." One such pattern is paradigmatic morphology, where complex words are built from the systematic use "and re-use" of sub-lexical units. Here, we provide evidence of emergent paradigmatic morphology akin to number inflection in a communication system developed without input from a conventional language, "homesign." We study the communication systems of four deaf child homesigners (mean age 8;02). Although these idiosyncratic systems vary from one another, we nevertheless find that all four children use handshape and movement devices productively to express cardinal and non-cardinal number information, and that their number expressions are consistent in both form and meaning. Our study shows, for the first time, that all four homesigners not only incorporate number devices into representational devices used as predicates, but also into gestures functioning as nominals, including deictic gestures. In other words, the homesigners express number by systematically combining "and re-combining" additive markers for number ("qua" inflectional morphemes) with representational and deictic gestures ("qua" bases). The creation of new, complex forms with predictable meanings across gesture types and linguistic functions constitutes evidence for an inflectional morphological "paradigm" in homesign and expands our understanding of the structural patterns of language that are, and are not, dependent on linguistic input.