Triquetra / Trinity Knot

Triquetra (/tra??kw?tr?/; Latin tri- "three" and quetrus "cornered") originally meant "triangle" and was used to refer to various three-cornered shapes. Nowadays, it has come to refer exclusively to a particular more complicated shape formed of three vesicae piscis, sometimes with an added circle in or around it. Also known as a "trinity knot," the design is used as a religious symbol by both Christians and polytheists.