3 goes into 9 exactly 3 times, so fractions with 3 in the denominator have a single digit repeating sequences in their decimal expansions. A natural number is divisible by three if and only if its decimal digit sum is divisible by 3. The same applies to nine, a number is divisible by 9, if its decimal digit sum is divisible by 9. In base-N, the divisors of N-1 have this property.
Many human cultures have given the concept of three-ness symbolic meanings:
- The Holy Trinity in Christian doctrine
- The process of synthesis in Hegelian dialectic creates three-ness from two-ness
- The three Doshas (weaknesses) and their antidotes are the basis of Ayurvedic medicine, for a complete system of medicine in India
- The three Gunas underlie action, in the Vedic system of knowledge.
- The Trimurti in Hindu tradition
Three is also:
- the number of musicians in a trio.
Other uses for three:
- Three's Company
- Three of a Kind
- Three: a rock band formed by Keith Emerson, Robert Berry and Carl Palmer.
This article is about the number. For the year AD 3, see 3.