[7]: 52  Two distinct points in a plane are always sufficient to define a unique line in a nontrivial Euclidean space.

[citation needed] Binary is a number system with a base of two, it is used extensively in computing.

[10] The digit used in the modern Western world to represent the number 2 traces its roots back to the Indic Brahmic script, where "2" was written as two horizontal lines.

The modern Chinese and Japanese languages (and Korean Hanja) still use this method.

The Gupta script rotated the two lines 45 degrees, making them diagonal.

In the Arabic Ghubar writing, the bottom line was completely vertical, and the digit looked like a dotless closing question mark.