Expressivity of hand movements is much greater than what current interaction techniques enable in touch-screen input. Especially for collaboration, hands are used to interact but also to express intentions, point to the physical space in which collaboration takes place, and communicate meaningful actions to collaborators. Various types of interaction are enabled by multi-touch surfaces (singe and both hands, single and multiple fingers, etc), and standard approaches to tactile interactive systems usually fail in handling such complexity of expresion. The diversity of multi-touch input also makes designing multi-touch gestures a difficult task. We believe that one cause for this design challenge is our limited understanding of variability in multi-touch gesture articulation, which affects users' opportunities to use gestures effectively in current multi-touch interfaces. A better understanding of multi-touch gesture variability can also lead to more robust design to support different users' gesture preferences. In this chapter we present our results on multi-touch gesture variability. We are mainly concerned with understanding variability in multi-touch gestures articulation from a pure user-centric perspective. We present a comprehensive investigation on how users vary their gestures in multi-touch gestures even under unconstrained articulation conditions. We conducted two experiments from which we collected 6669 multi-touch gestures from 46 participants. We performed a qualitative analysis of user gesture variability to derive a taxonomy for users' multi-touch gestures that complements other existing taxonomies. We also provide a comprehensive analysis on the strategies employed by users to create different gesture articulation variations for the same gesture type.