|The so-called "standard model" of the the definition of force, in modern terms, of which four varieties of forces, strong nuclear force, electromagnetic force, weak nuclear force, and the gravitational force, are said to account for all movements in the universe, and in which the mechanism of the force is said to operate via the exchange of field particles, messenger particles, or force carriers which come in four varieties: gluons, photons, bosons, and gravitons, which carry and transmit the force. |
In 1686, English physicist Isaac Newton, in his famed Principia, introduced the standard model of "force", as defined by his three laws of motion.
In 1834, Irish mathematical physicist William Hamilton, one of the founders of dynamics, the study of the motion of bodies under the action of forces, defines force or rather what he called the science of force as follows: 
The so-called standard model of science is that there are four types of fundamental forces:
1. Strong nuclear force – mediates subatomic interactions.The forth of these, namely gravity, however, can be shown to but a version of the electromagnetic force; hence, it can be argued that there are only three fundamental forces of the universe, as things currently stand.
2. Electromagnetic force – mediates atomic and molecular interactions.
3. Weak nuclear force – mediates radioactive decay processes.
4. Gravitational force – mediates interactions between objects with mass.
See main: Exchange forceIn modern terms, forces are said to be mediated by particles or entities called "force carriers" or field particles. 
In 1998, American NASA scientist John Anderson famously pointed out the "pioneer anomaly", namely that the Pioneer 10 and Pioneer 11 space probes that where launched in the early 1970s, but now powered-out are "decelerating" in a manner that cannot be accounted for by standard models of gravity. 
The 2007-2008 work of American electrochemical engineer Libb Thims, on the nature of the relation of the "chemical bond" existent between "human molecules" in relationships and the so-called "bond" that holds "human molecules" to the "earth molecule" and in turn the "earth molecule" to the "sun molecule" seems to indicate that the so-called gravitational force is a sort of large scale derivative of the electromagnetic force, although the details of this theory need to be worked out. 
In 2011, researchers at Fermilab, studying data on particle accelerator collisions from 2001 to 2009, announced the possibility of the data showing that a new force of nature exists, a hypothetical particle known as the Z’ boson, a heavier cousin of the Z boson, with a proposed mass of 150 billion electron volts, posited to be a new subset of the weak nuclear force set of exchange particles. 
The following are related quotes:
“Sometimes I think the force is stronger in the dead than in the living.”
|● Thermodynamic force|
● Driving force
● Entropic force
● Conservation of force
|● Social gravitation|
● Primary field particle
● Secondary field particle
● Motive force
1. Clark, John O.E. (2004). The Essential Dictionary of Science. New York: Barnes & Noble Books.
2. Ford, Kenneth W. (2004). The Quantum World, (pg. 46). Cambridge, Mass.: Harvard University Press.
3. Hamilton, W.R. (1834). “On a general method in dynamics by which the study of the motions of all free systems of attracting or repelling points is reduced to the search and differentiation of one central relation, or characteristic function.” Philos. Trans. R. Soc. London, 124:247-308.
4. (a) Cowen, Ron. (2011). “Pioneer Puzzle Pinned on Thermodynamics: New Study Declares Long-standing Mystery Solved, but Experts are Skeptical”, April 7th, ScienceNew.org.
(b) Cowen, Ron. (2008). “Pioneer 10’s Puzzling Motion: a Lot of Hot Air”, Science News Online, Apr 24.
(c) Cowen, Ron. (2008). “Too Speedy for Gravity? Science News. Vol. 173, Mar. 15, pg. 173.
5. Cowen, Ron. (2011). “Fermilab Data Hint at Possible New Particle: Powerful Collisions of Protons and Antiprotons Produced Unexplained Result.” April 6th, ScienceNews.org.
6. (a) Thims, Libb. (2007). Human Chemistry (Volume One) (fundamental forces, pg. 195-96). Morrisville, NC: LuLu.
(b) Thims, Libb. (2007). Human Chemistry (Volume Two). Morrisville, NC: LuLu.
(c) Thims, Libb. (2008). The Human Molecule (issuu) (preview) (Google Books) (docstoc). LuLu.
● Force – Wikipedia.