Structural superlubricity (SSL) is a fundamental tribological concept of ultralow sliding friction and negligible wear occurring at clean incommensurate interfaces, often formed between atomically flat, rigid, and weakly interacting crystalline surfaces. The geometric incommensurability may arise from either intrinsic lattice mismatch or rotational or strain misalignment of the contacting surfaces. Under these conditions, the lateral forces acting at different regions of the interface largely cancel each other, resulting in a dramatic reduction of friction during sliding. In the idealized limit of rigid and infinitely extended incommensurate interfaces, SSL corresponds to the complete absence of static friction. In real finite-size systems the observed static friction is nonzero and the most commonly used definitions of structural lubricity involve sub-linear scaling of static friction with contact area, and the kinetic friction coefficient (μ) falling below 10^-3. When μ<10^-2 in practical settings, the system is often described as exhibiting engineering superlubricity