The meaning of the symbol π π was not originally fixed to the ratio of the circumference and the diameter. In 1697, David Gregory used ⁠ π / ρ ⁠ (pi over rho) to denote the perimeter of a circle (i.e., the circumference) divided by its radius. However, earlier in 1647, William Oughtred had used ⁠ δ / π ⁠ (delta over pi) for the ratio of the diameter to perimeter. The first use of the symbol π on its own with its present meaning (of perimeter divided by diameter) was in 1706 by the Welsh mathematician William Jones.