## Wikipedia - Collision theory (en) Wikipedia - Teoría de las colisiones (es) Wikipedia - Théorie des collisions (fr) Wikipedia - Теорија за судирите (mk) collision frequency, $$z_{\text{A}}(\text{A})$$

https://doi.org/10.1351/goldbook.C01166
Average number of collisions experienced by a molecule A with other molecules A (or B) in a time interval divided by that time interval.
Source:
Green Book, 2nd ed., p. 56 [Terms] [Book]