The technical definition is a space devoid of any matter. In practice, it is very difficult to achieve a perfect vacuum, and levels of partial vacuum are more common. On Earth, ultra-high vacuum chambers can achieve 100 particles/cm³. Outer space has the equivalent of a few hydrogen atoms per cubic meter. Near-vacuum is sometimes used to describe the conditions in low earth orbit, where the conditions are not far from true outer space.

A connector orientation - the mating face of the connector is parallel and facing away from the PCB where the connector is mounted. Called Vertical because the housing stands vertical when the PCB is held flat.

A test criteria for mated connectors. A mated pair will be subject to a continuous steady shaking at a set acceleration, frequency and amplitude in each of the three axes (X, Y and Z, tested separately) and at the same time monitoring for any electrical discontinuity. Typically to pass a vibration test, the mated connectors should show no discontinuity for greater than 1µs (one micro-second or 10^-6 seconds), and should pass visual inspection.

The derived SI unit of electric potential difference (voltage), defined as the electric potential energy per unit charge. The symbol for volt is V, and is equivalent to joules per coulomb. The voltage between point A to point B is equal to the work which would have to be done, per unit charge, against or by the electric field to move the charge from A to B.

The volt is named in honor of the Italian physicist Alessandro Volta (1745–1827), who invented the voltaic pile, possibly the first chemical battery.

The electric potential difference between two points. The SI unit of voltage is the volt.