Greek letter that looks like "p"

RHO

This symbol often represents density in physics and follows pi in the alphabet.

The clue refers to the Greek alphabet, where letters often resemble English ones but have different names. "Rho" is the 17th Greek letter (Ρ, ρ), and its lowercase form looks almost identical to a handwritten or stylized "p." Since the clue hints at the shape rather than the sound, you focus on visual similarity—like how a "p" might appear in cursive or certain fonts. The answer isn’t "pi" (which sounds like "p" but looks different) or "mu," so "rho" fits perfectly.