part of a lamp which provides connection to the electrical supply by means of a lampholder or lamp connector and, in most cases, also serves to retain the lamp in the lampholder
Equivalent term used in the US: "base"
NOTE 1 The term "base" is used in both outside and in the US to denote an integral part of a lamp envelope which has been shaped so that it fulfils the function of a cap. It may engage also either a holder or a connector, depending on other design features of the lamp-and-holder system.
NOTE 2 The cap of a lamp and its corresponding holder are generally identified by one or more letters followed by a number which indicates approximately the principal dimension (generally the diameter) of the cap in millimetres. The standard code is to be found in IEC Publication 60061.