What does Lambda Mean in Physics?

Hint: Lambda's form and orientation changed in early Greek alphabets. The majority of variations were made up of two straight strokes, one longer than the other and linked at the ends. It's possible that the angle is in the upper-left or lower-left. A vertical line with a horizontal or sloping stroke going to the right was used in other variations. With the widespread use of the Ionic alphabet, Greeks chose a top-left angle, whereas Romans chose a lower-left angle.

Complete answer:
In physics, electrical engineering, and mathematics, lambda $\lambda $ denotes the wavelength of any wave.
In evolutionary algorithms, $\lambda $ specifies the number of children that would be produced in each generation from the current population. The terms come from the Evolutionary strategy notation.
In nuclear physics and radioactivity, $\lambda $ lambda denotes the radioactivity decay constant. This constant is directly proportional to the half-life of any radioactive substance (through a multiplicative constant).
The density of occurrences within a time interval, as predicted by the Poisson distribution, is represented by lambda $\lambda $ in probability theory.
Lambda $\lambda $ is a term used in the physics of electric fields to describe the linear charge density of a homogeneous line of electric charge (measured in coulombs per meter).
In multi-dimensional calculus, Lambda $\lambda $ signifies a Lagrange multiplier.
Lambda $\lambda $ is the channel length modulation parameter of a MOSFET in solid-state electronics.

Note: The wavelength of a periodic wave is its spatial period, or the distance over which the wave's form repeats. It's the distance between two adjacent corresponding points of the same phase on the wave, such two adjacent crests, troughs, or zero crossings, and it's a feature of both travelling and standing waves, as well as other spatial wave patterns.