has a plug. Where the relationship is equal, such as when two flexible cables are connected (an "inline" connection), each is considered a plug. Jacks use the reference designator prefix of J and plugs use the reference designator prefix of P. It is common practice to use female connectors for jacks, so the informal gender-based usage often happens to agree with the functional description of the technical standards. However, this is not always the case; often-seen exceptions include a computer's AC Power Inlet and EIA232 DE9 Serial Port, or the male coaxial power jacks for connecting external power adapters to portable equipment. To summarize, it is considered best practice to use "male" and "female" for connector gender, and "plug" and "jack" for connector function or mobility. Variant usages In the United Kingdom, many Commonwealth countries, and some non-English-speaking countries, the word "jack" may refer to the plug on the end of a removable cable. These connectors were originally referred to as "jack plugs", or plugs intended to be mated with fixed receptacles, or sockets (which North Americans would call "jacks"), but the second word was dropped. This variant usage is in direct contradiction to common usage and official standards in North America. For example in the UK, the connector on the end of a headphone lead is known as a "jack", that plugs into a socket on the main unit. The same usage also generally occurs in Italy, where the English word "jack" is commonly used to indicate the connector on the end of a headphone lead. In Romania, female connectors are known as mamă ("mother") and male connectors are tată ("father"). Abbreviations and alternate terminology The standard letters "M" and "F" are commonly used in part numbers to designate connector gender. For example, in Switchcraft XLR microphone or hydrophone connectors, the part numbers are denoted as follows: A3F = Audio 3-pin Female connector; A3M = Audio 3-pin Male connector. The terms plug, pin, and prong are also often used for "male" connectors, and receptacle, socket, and slot are used for "female" connectors. In many cases these terms are more common than male and female, especially in documentation intended for the non-specialist. These nearly synonymous terms can cause a fair amount of confusion when the designations are shortened in labels. For example, a female high-density D-subminiature connector with a size 1 shell can be named DE15F or DE15S (see accompanying