  We study the contribution to the entanglement entropy of (2+1)-dimensional
conformal field theories coming from a sharp corner in the entangling surface.
This contribution is encoded in a function $a(\theta)$ of the corner opening
angle, and was recently proposed as a measure of the degrees of freedom in the
underlying CFT. We show that the ratio $a(\theta)/C_T$, where $C_T$ is the
central charge in the stress tensor correlator, is an almost universal quantity
for a broad class of theories including various higher-curvature holographic
models, free scalars and fermions, and Wilson-Fisher fixed points of the $O(N)$
models with $N=1,2,3$. Strikingly, the agreement between these different
theories becomes exact in the limit $\theta\rightarrow \pi$, where the
entangling surface approaches a smooth curve. We thus conjecture that the
corresponding ratio is universal for general CFTs in three dimensions.
