Then some of the Greek letters have a life of their own beyond their mere existence as Greek letters. Pi, phi, and theta come to mind.
Yip. Exactly. We don't even think of them as Greek letters, per se. We use them interchangeably with typewriter symbols; however, because they are not easy to type, we often write 'phi' instead of using "insert symbol" or "insert special character" or "alt-1000" (Φ). Of course we use pi to represent the ratio of Circumference to Diameter, which was known to the ancient Greeks to be constant. Phi is often used to mean the Golden Ratio, but more often an angle in 3D polar coordinates (along with theta).
As you're aware, though, the same can't be of Romance symbols that are used like this, though! When we talk about the speed of light (SOL) in a vacuum, we write 'c' and not 'cee.' We talk about 'm' (for mass) and not 'em'. In one sense, this is inconsistent. However, in the sense that we are attempting to conserve keystrokes, it's consistent.
