Clarifying the landscape of mechanical sensors from stress to strain.

Stress and strain sensors are core measurement technologies used across a wide range of fields, including healthcare, environmental monitoring, aerospace and intelligent manufacturing. Although both capture aspects of mechanical behaviour, they are governed by distinct physical quantities: stress sensors measure internal mechanical stress, whereas strain sensors detect geometric deformation. Here, within the broader landscape of mechanical sensing, we discuss the differences between stress and strain sensors to clarify the common misconceptions that can obscure their distinctions, lead to misinterpretation in performance evaluation and affect sensor design. This Review establishes a unifying, mechanics-oriented framework that aligns sensing mechanisms, material systems and structural designs with stress-driven and strain-driven sensing pathways. It facilitates the mechanism-specific interpretation of performance metrics and integrates system-level considerations with artificial intelligence-assisted signal processing. The framework enables rational device design, reliable signal analysis and application-specific sensor selection, with relevance that extends beyond mechanical sensing.