One is the first positive integer and the first odd number; it is also known as unity. From the time of Euclid to the late 1500s, one wasn't generally considered to be a number but instead was thought of as the unit of which bona fide numbers were composed. The Old English (c.550–c.1100) ane served both for counting and as the indefinite article. Toward the end of the Old English period and the beginning of Middle English (c.1100-c.1500), ane developed two pronunciations, the first being used for 1 and the other for the indefinite article an, a. The existence of different words for the number one and the indefinite article seems to be unique to the English language. "One" can be traced back to the Latin unus and the Greek oine but probably came into English from the German eine.