An acid is deemed strong if it can readily or easy "donate" a proton (H+) to the other ions in the solutions. Also, to donate or lose the proton or H+, the acid must dissociate (split into ions) in the solution. The more it can readily dissociate, the stronger the acid is.
Strong acid is the acid that can absolutely dissociated in aqueous solution and weak acids are unlike the strong acids which cannot be dissociated or ionized in aqueous solution completely. Their dissociation power makes the acid strong or weak. If they dissociate completely then they will be strong and vice versa. Hydrochloric acid(HCl), H2SO4,etc are the strong acids and acetic acid(CH3COOH), lactic acid, etc are weak acids.
