Homonym: ре (Musical)
"Ре" is the 18th letter of the Cyrillic alphabet, used in languages such as Russian, Ukrainian, and Bulgarian. It represents the sound similar to the English "r" and is pronounced with a rolling effect. In the context of music, "ре" corresponds to the note D in the solfège system.
In mathematics, "ре" can refer to the mathematical constant π (pi) when transliterated into Cyrillic. This constant represents the ratio of a circle's circumference to its diameter and is approximately equal to 3.14. It is widely used in geometry, trigonometry, and various fields of science.