argon

 
Pronunciation: /ˈɑːgɒn/

noun

[mass noun]
  • the chemical element of atomic number 18, an inert gaseous element of the noble gas group. Argon is the commonest noble gas, making up nearly one per cent of the earth’s atmosphere. (Symbol: Ar)

Origin:

late 19th century: from Greek, neuter of argos 'idle', from a- 'without' + ergon 'work'