DeclarePoints[A1, ..., An]

A1, ..., An: names

The function DeclarePoints establishes the names A1, ..., An as point labels. A name may only be declared once as a point label.

The function DeclarePoints results in permanent changes to the global variable GlobalPointDeclarations.

Restart;
DeclarePoints[A,B,C];
GlobalPointDeclarations

$\left\{A\to \left\{\right\},B\to \left\{\right\},C\to \left\{\right\}\right\}$

DeclareObservers, DeclareTriads, DefinePoints