hafnium, Hf, atomic number
(noun) a grey tetravalent metallic element that resembles zirconium chemically and is found in zirconium minerals; used in filaments for its ready emission of electrons
Source: WordNet® 3.1
hafnium (uncountable)
A chemical element (symbol Hf) with an atomic number of 72: a lustrous, silvery-grey tetravalent transition metal.
• celtium (former name)
Source: Wiktionary
2 April 2025
(adjective) secret or hidden; not openly practiced or engaged in or shown or avowed; “covert actions by the CIA”; “covert funding for the rebels”
The first coffee-house in Mecca dates back to the 1510s. The beverage was in Turkey by the 1530s. It appeared in Europe circa 1515-1519 and was introduced to England by 1650. By 1675 the country had more than 3,000 coffee houses, and coffee had replaced beer as a breakfast drink.
