quantal
adjective
quan·tal ˈkwän-tᵊl 
1
[Latin quanti how many, plural of quantus] : of, relating to, or having only two experimental alternatives (such as dead or alive, all or none)
2
[quantum] : of or relating to a quantum
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Get Quantitative With Quantum
In Latin, quantum is the neuter form of quantus, meaning "how much?" Both of these forms played a role in the development of quantal. The first sense of quantal, used in scientific experimentation to refer to cases in which only one of two possible results occurs, derived from quanti, the plural of quantus. (Quantus is also an ancestor of our noun quantity.) The second sense of quantal is more directly related to Latin quantum and the English noun quantum, which refers to the smallest possible unit of a form of energy (such as light).
Word History
First Known Use
1933, in the meaning defined at sense 1
Medical Definition
quantal
adjective
quan·tal ˈkwänt-ᵊl
1
: of or relating to a quantum or to quanta (as of energy or a neurotransmitter)
quantal release of acetylcholine
2
: being or relating to a sensitivity response marked by the presence or absence of a definite reaction
an all-or-none response to a stimulus is quantal