# What does this vector notation mean

I was reading through the paper "Deformation Constraints in a Mass-Spring Model to Describe Rigid Cloth Behavior" and came across some vector notation that I am not familiar with. The notation in question is boxed in blue:

Initially I though that this meant the length between particle $P_{ij}$ and particle $P_{kl}$, but it is clearly a vector and not a scalar.

The vector $\vec{AB}$ is $B-A$.
$|\vec{AB}|$ is the distance between $A$ and $B$.
• Just to expound a bit more: it’s the vector that points from $P_{i,j}$ to $P_{k,l}$ $\ddot\smile$ – gen-z ready to perish Dec 17 '17 at 19:32