A primary star in a constellation isn't a specific term. There's no official designation like "primary star."

Here's why:

* Constellations are patterns: Constellations are groupings of stars that humans have imagined to form shapes or figures in the sky. They don't have inherent hierarchies within them.

* Brightness and importance: The brightest star in a constellation might be considered the most prominent, but that's based on its apparent magnitude (how bright it appears from Earth).

* Individual star names: Individual stars within constellations often have their own names (like Polaris, Sirius, or Vega) or Bayer designations (like Alpha Centauri, Beta Ursae Majoris).

In summary: While we might refer to the brightest star in a constellation as the most prominent, there's no official term like "primary star."