Acids that give high concentration of H+ ions on ionisation in aqueous solution are said to be strong acids and acids which give less H+ ions on ionisation in aqueous solution are said to be weak acids.
Weak acids are acids that don't completely dissociate in solution. In other words, a weak acid is any acid that is not a strong acid. The strength of a weak acid depends on how much it dissociates: the more it dissociates, the stronger the acid.
