In the oil and gas industry, a drill bit is a tool designed to produce a generally cylindrical hole (wellbore) in the earth’s crust by the rotary drilling method for the discovery and extraction of hydrocarbons such as crude oil and natural gas.

In physics a drift velocity is the average velocity attained by charged particles, such as electrons, in a material due to an electric field.

drift current is the electric current, or movement of charge carriers, which is due to the applied electric field, often stated as the electromotive force over a given distance.

This storage system uses a chamber with specific boundaries to store large amounts of air.

The storage vessel is kept at constant pressure, while the gas is contained in a variable-volume vessel.

A conservative force is a force with the property that the total work done in moving a particle between two points is independent of the path taken.

The law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be conserved over time.

A connecting rod is the part of a piston engine which connects the piston to the crankshaft.

In geology and sedimentology, connate fluids are liquids that were trapped in the pores of sedimentary rocks as they were deposited.

A confined space is a space with limited entry and egress and not suitable for human inhabitants.

An electrical conductor is a material that allows the free flow of elctrons through material such as metals.

Conductor clashing is the phenomenon where conductors come in contact with one another during high wind speeds or gusts.

Electrical conductivity is defined as how much voltage is required to get an amount of electric current to flow.

A conductive textile is a fabric which can conduct electricity.

Similar to firm service in that it is reserved and has priority over interruptible service.

Condition-based maintenance is maintenance when need arises. It is performed after one or more indicators show that equipment is going to fail or that equipment performance is deteriorating.

Condition monitoring is the process of monitoring a parameter of condition in machinery (vibration, temperature etc.), in order to identify a significant change which is indicative of a developing fault.

A heat exchanger in which hot, pressurized (gaseous) refrigerant is condensed by transferring heat to cooler surrounding air, water, or earth.

Concentrator photovoltaics is a photovoltaic technology that generates electricity from sunlight. Unlike conventional photovoltaic systems, it uses lenses or curved mirrors to focus sunlight onto small, highly efficient, multi-junction solar cells.

Condensation is the change of the physical state of matter from the gas phase into the liquid phase, and is the reverse of vaporization.