[Greek hēlios, sun.]
The Sun is at the centre of the solar system, which is therefore heliocentric; the heliosphere is the volume of space, enclosing the solar system, in which the solar wind has a significant influence. A heliograph is either a type of telescope for photographing the Sun, or a signalling device that reflects sunlight off a mirror. Heliotherapy is the therapeutic use of sunlight. Heliotrope (Greek trepein, to turn) is a plant of the borage family whose flowers turn towards the Sun; it has purple flowers, so the word can also refer to that colour. A beautiful variety of clear yellow beryl is called heliodor (literally ‘a gift from the Sun’, from Greek dōron, gift).