Proportional to sign (∝)

How to read it

OpenStax’s College Algebra calls a relationship in which one quantity is a constant multiplied by another direct variation, and says that y “varies directly with, or is proportional to” x; the constant, k, is the constant of variation. The IUPAC Green Book gives ∼ and ∝ as the two signs for “proportional to”, and Unicode names ∝ (U+221D) PROPORTIONAL TO. In physics it often says how one quantity depends on another before the constant is known: OpenStax’s University Physics notes that the area of a sphere is proportional to r², which is why gravity falls off with the square of the distance.

Also searched as: ∝, directly proportional to, proportionality symbol, proportional symbol, proportional to sign symbol, varies as.

Look-alikes

Unicode cross-refers ∝ to the Greek small alpha α, which it closely resembles; α is closed on the right where ∝ is open. With the gap closed it would be the infinity sign ∞. The Green Book’s other sign for “proportional to”, ∼, is a single wave, not the double wave of ≈, “approximately equal to”.