Tera is a unit prefix in the metric system denoting multiplication by 1012 or 1000000000000 (one trillion short scale; one billion long scale). It has the symbol T. Tera is derived from Greek word τέρας teras, meaning "monster". The prefix tera- was confirmed for use in the SI in 1960. Examples of its use: \n* terahertz radiation: electromagnetic waves within the band of frequencies from 0.3 to 3 THz \n* terabit, tebibit, terabyte and tebibyte, units used in data storage. \n* teragram: equal to 109 kg. The Great Pyramid of Giza has a mass of about 6 Tg. \n* terasecond: approximately 31,558 years \n* teralitre: equal to 109 m3. Lake Zurich contains about 4 TL of water. \n* terawatt: used to measure total human energy consumption. In 2010 it was 16 TW. \n* terametre (= 1,000,000,000 km): Light travels 1.079 Tm in one hour.