Arrival. A customer or item entering a line or queue for service or further processing.
Arrival distribution. The variability in the number of arrivals per some selected period of time. This variability can be represented by selected probability distributions to best fit the particular situation, with the Poisson distribution being most commonly used.
Arrival rate. The average number of arrivals per some selected period of time. This continuous value can have a decimal component for small arrival rates, but it is often rounded to whole numbers for larger rates. This value is represented by the Greek lambda (λ) in waiting line equations. Some typical values are 30 products per day, 18 customers per hour, or 1.6 cars every ...