tetra

Everyday

1. A tetra is a small, often brightly coloured freshwater fish from South America or Africa, popular in home aquariums, such as the neon tetra. tree →
2. Tetra- at the start of a word means four, as in tetrahedron (a solid with four faces) and tetrapod (an animal with four limbs). tree →

In the lessons

In everyday life tetras are pet fish kept in tanks. In maths and science the prefix tetra- signals the number four. Phrases: neon tetra, a shoal of tetras, tetrahedron.

Examples

• We have six neon tetras in our fish tank. tree →
• Tetras like to swim together in a shoal. tree →
• A tetrahedron is a pyramid with four triangle faces. tree →
• The neon tetra has a shiny blue stripe. tree →
• Frogs, lizards, birds and people are all tetrapods. tree →
• Feed the tetras a small pinch of flakes. tree →
• The pet shop sells tetras, guppies and goldfish. tree →

Note

Countable: one tetra, two tetras. In maths, tetra- = 4 (tri- = 3, penta- = 5). Tetra Pak is a brand name for drink cartons, not a fish.

In Jewish tradition

In everyday life tetras are pet fish kept in tanks. In maths and science the prefix tetra- signals the number four. Phrases: neon tetra, a shoal of tetras, tetrahedron.

Examples

• Rittangelius gives "credidit in Tetra- grammaton," but this word is not in the Hebrew. (Sefer Yetzirah, Westcott 1893) tree →
• The vowel letters, however, the letters of the Tetra- grammaton, are images and pictures of superior angels. (Mordell, The Origin of Letters and Numerals according to Sefer Yetzirah (1914)) tree →

Note

Countable: one tetra, two tetras. In maths, tetra- = 4 (tri- = 3, penta- = 5). Tetra Pak is a brand name for drink cartons, not a fish.