l - litre, a derived SI unit of volume.

Lagrangian measurement - Observation of a current with a device flowing with the current.

Laminar Flow - Streamlined flow of a fluid where viscous forces are more significant than inertial forces, generally below a
Reynolds number of 2000.

LAN - Local Area Network: A computer network that connects computers, file and mail servers, storage, perpipherals, and
other devices in a way that permits data interchange and sharing of resources.

Lance-Wood - An elastic wood suitable where some degree of bending is required.

Land - That surface on the periphery of a rotary cutting tool, such as a milling cutter, drill, tap, or reamer, which joins the face
of the flute or tooth to make up the basic cutting edge.

Lantern ring - The portion of the stuffing box (on a pump) which provides a seal around the impeller shaft where it enters the
pump casing.

Lap - A tool made of soft metal and charged with fine abrasives for precision finishing of metal surfaces.

Lap Joint - A joint between two overlapping members.

Laplace equation - The partial differential equation governing steady-state flow in a homogeneous, isotropic aquifer.

Lapping - A surface finishing operation used to achieve a fine polish and close tolerances.

Larch - An extremely durable wood used for rough work. It warps a lot when dried, but can be polished to a fine finish when

Large Scale Integration (LSI) - Refers to the number of logic gates in a device. Large scale integration represents a device
containing 100 to 999 gates.

Last In First Out (LIFO) - A memory device in which data is read out in the reverse order to which it was written in.

Latent Heat - The thermal energy absorbed or released when a material experiences a phase change.

Latten - Elizabethan term for brass, probably of Dutch origin.

Leachate - Precipitation that comes into contact with contaminants in soil, such as the solid waste in a landfill.

Lead Hole - A starting hole for large drills to serve as a guide.

Lead - The lead of a helical gear tooth is the axial advance resulting from one full revolution of the helix on the cylinder.

Leaf Springs - Either a simple beam used as a spring or laminations of steel.

LCD - Liquid-crystal display

LED - Light-Emitting Diode

LEED - Leadership in Energy and Environmental Design,  a voluntary, nationally accepted benchmark for the design,
construction, and operation of high performance green buildings.

Left Hand Thread - A screw thread that is screwed in by rotating counterclockwise.

Letter Drills - This system of numbering drills is no longer used, but may be of use in deciphering old drawings.

Lever - One of the basic tools that date from prehistoric times.

Lift - The lifting force on a flying object.

Lift Coefficient - A dimensionless value that allows the comparison of lift incurred by different sized and different shaped
bodies. A positive lift coefficient represents lift, whilst a negative lift coefficient represents downforce.

Lifting Body - An aircraft that uses the shape of its body to generate lift instead of using wings.

Light Water Reactor - The most common type of nuclear reactor in the world. Uses light water (ordinary water) as a
moderator (to slow down neutrons in the reactor) and a coolant.

Lignum Vitae - A very hard wood.

Line of Action - The line of action of a force is the infinite line defined by extending along the direction of the force from the
point where the force acts.

Linearity - The maximum deviation of the calibration curve from a straight line between zero and full scale, expressed as a
percent of full scale output and measured on increasing measured only.

Lip of a Drill - The sharp cutting edge on the end of a twist drill.

Liquidated Damages - The cost a contractor is assessed if work is not completed by a pre-determined date.

Liquidus - In a constitution or equilibrium diagram, the locus of points representing the temperatures at which the various
compositions in the system begin to freeze on cooling or to finish melting on heating.

Liquified Gas -The liquid form of a substance which under normal conditions of temperature and pressure is found as a gas.

Usually applied to the liquid form of substances which under normal conditions of temperature and pressure are found as

litres per 100km - Unit of fuel consumption used in the automotive industry.

Live Centre - A centre that revolves with the work.

LNG - Liquefied natural gas

Load - The weight supported by a structure.

Local Stress Relieving - Stress relieving heat treatment of a specific portion of a structure.

Locking Pliers - A type of pliers with locking jaws that can be used as pliers, wrench, clamp, or small vice.

Logarithm - The exponent that indicates the power to which a number must be raised to produce a given number.

Logarithmic Scale - A method of displaying data (in powers of ten) to yield maximum range while keeping resolution at the
low end of the scale.

Long Nose Pliers - Pliers with half round and tapered jaws.

Lost Wax - Also known as investment or precision casting, it is based on the use of a mould that is only used once.

Lower Explosive Limit (LEL) - The concentration of a gas below which the concentration of vapors is insufficient to support an

LPG - Liquidified Petroleum Gas

Luder Bands - Elongated surface markings or depressions in sheet metal caused by discontinuous yielding.
Engineering Glossary, Engineering Dictionary L
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