<p><strong>Noun</strong></p><ul><li>(plural pis)<ul><li>the 16th letter of the Greek alphabet (Π, π).</li><li>the consonant sound represented by this letter.</li><li>Mathematics: the letter π, used as the symbol for the ratio of the circumference of a circle to its diameter.</li><li>the ratio itself: 3.141592.</li></ul></li></ul><p><strong>End of Response</strong></p>