(Uniform motion is motion in a straight line at a constant speed i.e. constant velocity).
So a force is any action that will change the uniform motion of a body.
Forces can also change the shape, momentum, impulse, rotation spin or energy of a body.
In Physics the current classification of Force is: Gravity, Strong Nuclear, Weak Nuclear and Electromagnetic.
An ongoing goal is to combine these into one super force. The Electric and Magnetic Forces were successfully combined in the 19th Century by James Clerk Maxwell. The Weak Nuclear and Electromagnetic Forces were combined in the early 1960 by the work of Sheldon Glashow, Abdus Salam, Steven Weinberg and others. This combined force is called the Electroweak Force.