(Subscriber Identity Module)- A chip smaller than a man’s thumbnail, which contains the number and network subscription of a mobile phone, and sometimes other data. Move the chip to another phone, and the phone number moves with it. A simfree phone is one bought without a number and not tied to any particular network. There are currently three types of different sizes. The standard SIM is the largest, used in older phones, the smaller micro- and nano-SIMs are used in the latest smartphones.