A computer mouse (plural mice, rarely mice) is a hand-held pointing device that detects two-dimensional motion relative to a surface. This movement is typically translated into the movement of a pointer on a screen, which allows for smooth control of a computer’s graphical user interface.
The first public demonstration of a mouse controlling a computer system was in 1968. Mice initially used two separate wheels to track movement across a surface; one in X size and the other in Y size. Later, the standard design changed to use a ball rolling on a surface to detect motion. Most modern mice use optical sensors with no moving parts. Although originally all mice were connected to a computer with a cable, some modern mice are wireless and rely on short-range radio communication with the connected system.
In addition to moving a cursor, computer mice have one or more buttons to allow operations such as selecting a menu item on a screen. Mice often also have other elements that provide additional control and size input, such as touchpads and scroll wheels.
A computer mouse is named because of its similarity to a rodent.
The earliest known written use of the term mouse to refer to a computer pointing device is in Bill English’s July 1965 publication, “Computer-Assisted Image Control,” possibly due to the similarity of a mouse in shape and size to a rodent. tail-like cord.    The popularity of wireless wireless mice makes the similarity less obvious.
The plural for small rodent is always “mouse” in modern usage. The plural for a computer mouse is “mice” or “mice” according to most dictionaries, and “mice” is more common.  The first recorded plural usage is “mouse”; Oxford Dictionaries online refers to a use in 1984, and earlier uses include JCR Licklider’s 1968 “The Computer as a Communication Device”. 
Inventor Douglas Engelbart holding the first computer mouse,  showing the wheels in contact with the work surface
The trackball, the related pointing device, was invented in 1946 by Ralph Benjamin as part of a post World War II-era fire control radar circling system, called the Comprehensive Display System (CDS). Benjamin was then working for the British Royal Naval Science Service. Benjamin’s project used analog computers to calculate the future position of the target aircraft based on several initial entry points provided by a user with a joystick. Benjamin felt the need for a more elegant input device and invented what they called the “roller ball” for this purpose.  
The device was patented in 1947  but only a prototype was built using a metal ball rotating on two rubber-covered wheels and the device was kept a military secret