Deuterium-depleted water is water which has a lower concentration of deuterium than occurs naturally on Earth.

Light tubes (also known as light pipes or tubular skylights) are physical structures used for transmitting or distributing natural or artificial light for the purpose of illumination, and are examples of optical waveguides.

Light fuel oils or diesel oils are high value distillates that have traditionally been used to fuel diesel engine power plants, both for stand-by operation and baseload applications.

Light crude oil is liquid petroleum that has a low density and flows freely at room temperature.

Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be perceived by the human eye.

A lifting body is a foil or a complete foil-bearing body such as a wind turbine blade.

A ratio of the two aerodynamic forces, lift and drag. A high lift-to-drag ratio is required for efficient blade design.

The lift coefficient is a dimensionless coefficient that relates the lift generated by a lifting body to the fluid density around the body, the fluid velocity and an associated reference area.

A fluid flowing around the surface of an object exerts a force on it.

Meaning the full age of a process or system from creation to decline.

Measurement of life-cycle greenhouse gas emissions involves calculating the global-warming potential of energy sources through life-cycle assessment.

Life-cycle assessment or LCA is a methodology for assessing environmental impacts associated with all the stages of the life-cycle of a commercial product, process, or service.

A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum.

The levelized cost of storage (LCOS) is the analogous of LCOE applied to electricity storage technologies, such as batteries.

The levelized cost of energy (LCOE), or levelized cost of electricity, is a measure of the average net present cost of electricity generation for a generating plant over its lifetime.

Level sensors detect the level of liquids and other fluids and fluidized solids, including slurries, granular materials, and powders that exhibit an upper free surface.

Level of measurement or scale of measure is a classification that describes the nature of information within the values assigned to variables.

A levee is an elongated naturally occurring ridge or artificially constructed fill or wall that regulates water levels.

Length is a measure of distance.

A lemon battery is a simple battery often made for the purpose of education.