In the mathematical theory of probability

Probability

Probability is ordinarily used to describe an attitude of mind towards some proposition of whose truth we arenot certain. The proposition of interest is usually of the form "Will a specific event occur?" The attitude of mind is of the form "How certain are we that the event will occur?" The...

, offered load is a concept in queuing theory. The offered load is a measure of traffic in the queue. The offered load is given by Little's law

Little's law

In the mathematical theory of queues, Little's result, theorem, lemma, law or formula says:It is a restatement of the Erlang formula, based on the work of Danish mathematician Agner Krarup Erlang...

: the arrival rate into the queue (symbolized with λ

Lambda

Lambda is the 11th letter of the Greek alphabet. In the system of Greek numerals lambda has a value of 30. Lambda is related to the Phoenician letter Lamed . Letters in other alphabets that stemmed from lambda include the Roman L and the Cyrillic letter El...

) multiplied by the mean holding time (symbolized with τ

Tau

Tau is the 19th letter of the Greek alphabet. In the system of Greek numerals it has a value of 300.The name in English is pronounced , but in modern Greek it is...

), the average amount of time spent by items in the queue. Offered load is expressed in Erlang unit

Erlang unit

The erlang is a dimensionless unit that is used in telephony as a statistical measure of offered load or carried load on service-providing elements such as telephone circuits or telephone switching equipment. It is named after the Danish telephone engineer A. K...

s, a dimensionless measure.