Units of measurement and currency

L, Langmuir (unit), a unit of exposure to a surface
L, length in general (often the longest dimension, as opposed to width, height, or depth)
- Horse length, used in horse racing
- Boat length, used in rowing
L, l or ℓ, litre unit
Ancient Roman libra (translated as "pound"), a weight measure with derivative units denoted with "L" or a derived character:
- Pound (currency), a number of currencies from the British Empire, abbreviated £ or (historically) "l", "L", or " ${\mathfrak {L))$ ". (Some fonts use a two-bar version resembling the lira sign ₤.)
- Livre (disambiguation), a number of currencies from the French Empire, with the original abbreviated "£", "₶", or "lt"
- Lira, a number of currencies from Italy and the Ottoman Empire, abbreviated as ₤
Leaf (books) ("l." or ℓ), an alternate numbering for books, in contrast to "p." for pages
Specification for a line of text, for example "l. 3" is the third line of text

Science

L, constructible universe, a particular class of sets which can be described entirely in terms of simpler sets
L-function
Laplace transform
${\mathcal {L))$ , likelihood function
ℓ^p space, the space of sequences with a finite p-norm
L^p space, a function space defined using a natural generalization of the p-norm for finite-dimensional vector spaces

L (complexity), a complexity class in computational complexity theory
L-notation, a notation for running times of subexponential algorithms, often used in number theory
L – A Mathemagical Adventure, a 1984 computer game
Android L, code name for Android Lollipop

Angular momentum
Inductance, the ratio of the magnetic flux to the current in an electrical circuit
Latent heat
Luminosity
Mean free path, the average distance traveled by a moving particle between successive collisions
Class L, a stellar classification
Galactic longitude (l), in the galactic coordinate system

Carl Linnaeus, in botanist author citations (L.)
Laelia, an orchid genus
Haplogroup L (Y-DNA)
Vertebra in the lumbar region of the spinal cord
ATC code L Antineoplastic and immunomodulating agents, a section of the Anatomical Therapeutic Chemical Classification System

L (French singer), French singer-songwriter
L (South Korean singer), vocalist of Korean boy band Infinite
L Marshall, British singer credited as L on the Wretch 32 song "Traktor"
Lesure Number, music catalogue identifier for the compositions of Claude Debussy
L Number, classification of the compositions of Franz Benda according to the catalogue of Douglas A. Lee

L (Los Angeles Railway)
Chicago "L", a rapid transit system in Chicago
L (New York City Subway service)
L Line (Los Angeles Metro)
Transilien Line L, a line of the Paris transport network
The official West Japan Railway Company service symbol for:
- Maizuru Line.
- Uno Line.
L-plate, a plate for learning drivers under instruction
L Taraval (San Francisco Muni)
Nissan L engine
L, the low gear of an automatic transmission
LB&SCR L class, a British tank locomotive on the London, Brighton, and South Coast Railway

L. Inc., California-based corporation that makes organic personal care products
Liberals (Sweden), a political party in Sweden
Loews Corporation, by NYSE ticker symbol
Miscellaneous, when used as the fifth letter or behind-the-dot notation on the NASDAQ and NYSE ticker symbols