Noun

(-)

The rubbing of one object or surface against another.

* {{quote-magazine, year=2013, month=July-August, author=(Henry Petroski)

, title= Geothermal Energy , volume=101, issue=4, magazine=(American Scientist) , passage=Energy has seldom been found where we need it when we want it. Ancient nomads, wishing to ward off the evening chill and enjoy a meal around a campfire, had to collect wood and then spend time and effort coaxing the heat of friction out from between sticks to kindle a flame.}}

Conflict, as between persons having dissimilar ideas or interests; clash.

(physics): A force that resists the relative motion or tendency to such motion of two bodies in contact.

* 1839 , (Denison Olmsted), A Compendium of Astronomy Page 95

Secondly, When a body is once in motion it will continue to move forever, unless something stops it. When a ball is struck on the surface of the earth, the friction of the earth and the resistance of the air soon stop its motion.

Noun

(countable, and, uncountable) An ache or bodily suffering, or an instance of this; an unpleasant sensation, resulting from a derangement of functions, disease, or injury by violence; hurt.

The greatest difficulty lies in treating patients with chronic pain .

I had to stop running when I started getting pains in my feet.

(uncountable) The condition or fact of suffering or anguish especially mental, as opposed to pleasure; torment; distress; sadness; grief; solicitude; disquietude.

In the final analysis, pain is a fact of life.

The pain of departure was difficult to bear.

(countable) An annoying person or thing.

Your mother is a right pain .

(uncountable, obsolete) Suffering inflicted as punishment or penalty.

You may not leave this room on pain of death.

Interpose, on pain of my displeasure. — Dryden

We will, by way of mulct or pain , lay it upon him. — Bacon

Labour; effort; pains.