Leeward is the direction downwind (or downward) from the point of reference.

An LED lamp or LED light bulb is an electric light that produces light using light-emitting diodes (LEDs). LED lamps are significantly more energy-efficient than equivalent incandescent lamps and can be significantly more efficient than most fluorescent lamps. The most efficient commercially available LED lamps have efficiencies of 200 lumens per watt (Lm/W).

Lean-burn gas engines is a spark-ignited lean-burn engine where the gas is mixed with air before the inlet valves.

A combustion process that increases the air to fuel ratio in order to reduce NOx in the exhaust.

The edge of a turbine blade that faces toward the direction of rotation.

The lead-cooled fast reactor is a nuclear reactor design that features a fast neutron spectrum and molten lead or lead-bismuth eutectic coolant.

The lead–acid battery is the earliest type of rechargeable battery.

Lead shielding refers to the use of lead as a form of radiation protection to shield people or objects from radiation so as to reduce the effective dose.

A lattice tower or truss tower is a freestanding vertical framework tower.

Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process.

Tanks that can be built on surface and covered with soil.

Laser isotope separation, or laser enrichment, is a technology of isotope separation using selective ionization of atoms or molecules by the means of precisely tuned lasers.

The Large Hadron Collider (LHC) is the world's largest and highest-energy particle collider and the largest machine in the world.

A collection of methods used for energy storage on a large scale within an electrical power grid.

Larderello is a frazione of the comune of Pomarance, in Tuscany in central Italy, renowned for its geothermal productivity.

Decarbonization refers to the reduction or elimination of carbon dioxide from energy sources.

The decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations.

A deaerator is a device that removes oxygen and other dissolved gases from liquids and pumpable compounds.

In law and government, de jure describes practices that are legally recognised, regardless of whether the practice exists in reality.

A de facto standard is a custom or convention that has achieved a dominant position by public acceptance or market forces.