What is the difference between concentrated acid and a weak one?

Difference between concentrated acid and weak acid :---

According to Arrhenius's theory the substances which easily get dissociated into H+ ions when dissolved in water are acids.And the substance which readily gives H+ ions on dissociation (when dissolved in water) are Strong Acid. Examples are HCl , H2SO4 etc.

While,

Concentration of acid is just the value of pH. pH is the measurement of concentration of acid or base. The lower the pH, higher the concentration.So strong acid is strong because it gives H+ ions readily in water and Concentration is the value of pH.