In a code, I am writing a concise documentation of a function that needs 2 vectors defining a triangle $ABC$. The function performs an operation which is invariant up to a translation, so two vectors only are necessary, named $\vec{s}$ and $\vec{z}$, and introducing points $A$, $B$ and $C$ is irrelevant and could even be misleading. However, the triangle $ABC$ has to be such that $[AB]$ is part of a polygonal chain (called polyline in computer science context) that is defined elsewhere in the code and $C$ of another. The function has little meaning independently of that setting.
I first document the properties of $\vec{s}$ as being one vector of the first polyline. Then I need to document $\vec{z}$, for that it would be convenient to say that $\vec{z}$ is such that $A+\vec{z}$ is a point of the other polyline.
s: vector, base of triangle, along polyline Γ_1
However, not having given $A$ a name, I'm struggling, even when tolerating some abuse of notation:
z: vector, pointing from [point of origin of] s along Γ_1 and to a point of Γ_2
Ιs there some elegant way to phrase this? Maybe
z: vector, pointing from Γ_1 and to Γ_2, with (s,z) an angle.
...although again, it would properly be $(A,\vec{s},\vec{z})$ an angle.