lambda
noun
lamb·da ˈlam-də 
1
: the 11th letter of the Greek alphabet see Alphabet Table
2
: an uncharged unstable elementary particle that has a mass 2183 times that of an electron and that decays typically into a nucleon and a pion
Word History
Etymology
Middle English, from Greek, of Semitic origin; akin to Hebrew lāmedh lamed
First Known Use
15th century, in the meaning defined at sense 1
Medical Definition
lambda
noun
lamb·da ˈlam-də
1
: the point of junction of the sagittal and lambdoid sutures of the skull
2
: bacteriophage lambda