## Wikipedia - Teoría de las colisiones 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]
See also:
PAC, 1996, 68, 149. (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 159 [Terms] [Paper]