In this paper we study several non-Riemannian quantities in Finsler geometry. These non-Riemannian quantities play an important role in understanding the geometric properties of Finsler metrics. In particular, we study a new non-Riemannian quantity defined by the $\text{S}$-curvature. We show some relationships among the flag curvature, the $\text{S}$-curvature, and the new non-Riemannian quantity.