The number one is a noun and defined as the first whole number above zero; however, the word one can also be used as an adjective or pronoun. The number one was first used around the 12th century, this word derives from the English word an, and the word an is derived from the Proto-Indo-European root *oi-no-. Many European languages have similar roots for the word one such as Gothic ains, Danish en, Greek oinos, and Latin unus.
As a digit, one is represented as a single vertical line with a serif at the top and sometimes a short horizontal line at the bottom “1”. This symbol can be traced back to India. In addition, in Roman numerals the number 1 is also represented as a single line since the single line is supposed to represent a single finger. Usually referred to as Arabic numerals, the symbol “1” reached Europe during the Middle ages.
Editing by Christina 