collision

A collision is an isolated event in which two or more moving bodies (colliding bodies) exert forces on each other for a relatively short time.
Although the most common colloquial use of the word "collision" refers to accidents in which two or more objects collide, the scientific use of the word "collision" implies nothing about the magnitude of the forces.
Some examples of physical interactions that scientists would consider collisions:

• An insect touches its antenna to the leaf of a plant. The antenna is said to collide with leaf.
• A cat walks delicately through the grass. Each contact that its paws make with the ground is a collision. Each brush of its fur against a blade of grass is a collision.

Some colloquial uses of the word collision are:

• automobile collision, two cars colliding with each other
• mid-air collision, two planes colliding with each other
• ship collision, two ships colliding with each other