1) In wireless telephony, a cell is the geographical area covered by a cellular telephone transmitter. The transmitter facility itself is called the cell site. The cell provided by a cell site can be from one mile to twenty miles in diameter, depending on terrain and transmission power. Several coordinated cell sites are called a cell system. When you sign up with a cellular telephone service provider, you generally are given access to their cell system, which is essentially local. When travelling out of the range of this cell system, the cell system can enable you to be transferred to a neighboring company's cell system without your being aware of it. This is called roaming service.
The cell sites in a system connect to a Mobile Telephone Switching Office (MTSO), which in turn connects to the standard landline telephone system.
2) In a battery power source, a cell is a single energy or charge-storing unit within a pack of cells that form the battery. Each cell has a voltage rating that is combined with the other cells' voltages to form the overall battery voltage rating.
3) In spreadsheet applications, a cell is a box in which you can enter a single piece of data. Spreadsheet cells are also referred to as data fields.