Lambda indicates the radioactivity decay constant in nuclear physics and radioactivity. This constant is very simply related (by a multiplicative constant) to the half-life of any radioactive material.
In ecology, lambda denotes the long-term intrinsic growth rate of a population. This value is often calculated as the dominant eigenvalue of the age/size class matrix (mathematics).
Lambda denotes the failure rate of devices and systems in reliability theory, and it is measured in failure events per hour. Numerically, this lamba is also the reciprocal of the Mean time between failures.
Lambda is used as a symbol for separating the two human breasts in Internet chat iconography, specifically as " ( . λ . ) "
In criminology, lambda denotes an individual's frequency of offense.
In Volvo automobiles, lambda denotes an engine, fuel, or ignition system failure.