An X mark is a mark used to indicate the concept of negation (for example "no, this has not been verified" or "no, I don't agree") as well as an in... See more

In mathematics, a square root of a number a is a number y such that y2 = a; in other words, a number y whose square (the result of multiplying the ... See more

In addition to being the 18th letter of the Greek alphabet, sigma also means 'sum' and 'deviation' in themathematics world. See more

The plus sign is written as a cross of horizontal and vertical lines: + The plus sign indicates addition operation of 2 numbers or expressions. See more

It is approximately equal to 3.14159. It has been represented by the Greek letter "π" since the mid-18th century, though it is also sometimes spell... See more

The triangular Deathly Hallows symbol is comprised of theElder Wand, the Resurrection Stone and the Cloak of Invisibility. Whoever possesses all th... See more

This traffic sign indicates that left turns are prohibited. See more

The Sign of the Deathly Hallows is a triangular mark used as a representation of the Deathly Hallows, three legendary objects that allegedly, if un... See more

A road signal for directing vehicular traffic by means of colored lights, typically red for stop, green for go, and yellow for proceed with caution. See more

This sign is used where parking is prohibited. See more

Fire Exit Signs and Emergency Exit Signs direct people to the proper exits in a fire emergency. See more

The Fallen Rocks sign indicates to drivers that they are approaching an area which is susceptible to falling rock or landslides, and that fallen ro... See more