3 (three) is a number, numeral and digit. It is the natural number following 2 and preceding 4, and is the smallest odd prime number and the only prime preceding a square number. It has religious or cultural significance in many societies. Evolution of the Arabic digit
The use of three lines to denote the number 3 occurred in many writing systems, including some (like Roman and Chinese numerals) that are still in use. That was also the original representation of 3 in the Brahmic (Indian) numerical notation, its earliest forms aligned vertically. However, during the Gupta Empire the sign was modified by the addition of a curve on each line. The Nāgarī script rotated the lines clockwise, so they appeared horizontally, and ended each line with a short downward stroke on the right. In cursive script, the three strokes were eventually connected to form a glyph resembling a ⟨3⟩ with an additional stroke at the bottom: ३. The Indian digits spread to the Caliphate in the 9th century. The bottom stroke was dropped around the 10th century in the western parts of the Caliphate, such as the Maghreb and Al-Andalus, when a distinct variant ("Western Arabic") of the digit symbols developed, including modern Western 3. In contrast, the Eastern Arabs retained and enlarged that stroke, rotating the digit once more to yield the modern ("Eastern") Arabic digit "٣".In most modern Western typefaces, the digit 3, like the other decimal digits, has the height of a capital letter, and sits on the baseline.
Protoscience
In European alchemy, the three primes (Latin: tria prima) were salt (), sulfur () and mercury (). The three doshas (weaknesses) and their antidotes are the basis of Ayurvedic medicine in India. Pseudoscience
Three is the symbolic representation for Mu, Augustus Le Plongeons and James Churchwards lost continent. In Pythagorean numerology the number 3 is the digit that represents the communication. It encourages the expansion of creativity, sociability between people and movement. For Pythagoras, the number 3 was a perfect number, representing harmony, perfection, and divine proportion. Philosophy
Philosophers such as Aquinas, Kant, Hegel, C. S. Peirce, and Karl Popper have made threefold divisions, or trichotomies, which have been important in their work. Hegels dialectic of Thesis + Antithesis = Synthesis creates three-ness from two-ness. Religion
Many world religions contain triple deities or concepts of trinity, including:

The Hindu Trimurti
The Hindu Tridevi
The Three Jewels of Buddhism
The Three Pure Ones of Taoism
The Christian Holy Trinity
The Triple Goddess of Wicca

Christianity
The threefold office of Christ is a Christian doctrine which states that Christ performs the functions of prophet, priest, and king. The ministry of Jesus lasted approximately three years. During the Agony in the Garden, Christ asked three times for the cup to be taken from him. Jesus rose from the dead on the third day after his death. The devil tempted Jesus three times. Saint Peter thrice denied Jesus and thrice affirmed his faith in Jesus. The Magi – wise men who were astronomers/astrologers from Persia – gave Jesus three gifts. There are three Synoptic Gospels and three epistles of John.