quan·ti·ty 
/ˈkwɑ:ntəti/ noun
plural quan·ti·ties /ˈkwɑ:ntəti/ noun 1 : an amount or number of something [count] ▪ The wine is made in small/large quantities. — often + of ▪ I ate a large quantity of food. [=I ate a lot of food] ▪ Farmers grow large quantities of wheat and corn. ▪ Add a half a cup of oil, and the same quantity of vinegar. [noncount] ▪ The boss is worried about quantity as well as quality. ▪ Production saw an increase in quantity. [=there was an increase in the amount produced] — abbr. qty. 2 : a large amount or number of something [count] — + of ▪ Police found quantities of drugs and guns in the house. ▪ There is a quantity of information [=a lot of information] available on this topic. [noncount] ▪ Blood cells are produced in quantity. [=in large amounts] ▪ The family buys food in quantity.
known quantity
: someone or something whose abilities or characteristics are well known
▪ When she was cast in the role of the princess, she was already a known quantity from her work in several films.
▪ When she was cast in the role of the princess, she was already a known quantity from her work in several films.
unknown quantity
: someone or something whose abilities or characteristics are not yet known
▪ If you've never been published before, you're an unknown quantity, so you're going to have difficulty selling your first novel.
▪ If you've never been published before, you're an unknown quantity, so you're going to have difficulty selling your first novel.
