* Primary: Directly from "primus."
* Primate: The first or highest in rank (e.g., primate in the church hierarchy, or a primate in the animal kingdom).
* Prime: First in importance, excellence, or quality; also a prime number in mathematics.
* Primogeniture: The right of the eldest child (typically son) to inherit property.
* Premier: First in rank, importance, or position.
* Primigenial: Original; belonging to the beginning; primitive.
* Primitive: Original, early, or simple in form; existing in or at an early stage of development.
Note that some words derived from "primus" may not be immediately obvious due to changes in spelling and pronunciation over time.