The word 'Acid' came from Latin word 'Acidus or Acere' which means sour.
Sour taste is the most common characteristic of acid. Acid turns blue litmus paper red. There are many substances which contain acid and hence taste sour, such as curd, tamarind, lemon, etc.
Acids give hydrogen gas along with respective salt when they react with a metal.
Metal+Acids->Salts+hydrogen gas
