An oxygen sensor (or lambda sensor, where lambda refers to air–fuel equivalence ratio, usually denoted by λ) or probe or sond, is an electronic device that measures the proportion of oxygen (O2) in the gas or liquid being analysed.
A three-wire oxygen sensor suitable for use in a Volvo 240 or similar vehicle
An oxygen analyser for breathing gas mixtures for diving
Lambda is the eleventh letter of the Greek alphabet, representing the voiced alveolar lateral approximant IPA: [l]. In the system of Greek numerals, lambda has a value of 30. Lambda is derived from the Phoenician Lamed. Lambda gave rise to the Latin L and the Cyrillic El (Л). The ancient grammarians and dramatists give evidence to the pronunciation as (λάβδα) in Classical Greek times. In Modern Greek, the name of the letter, Λάμδα, is pronounced.
The Greek alphabet on a black figure vessel, with a Phoenician-lamed-shaped lambda. The gamma has the shape of modern lambda.