Any hydrogen-containing material capable of transferring a proton (hydrogen ion) to another chemical is classified as an acid.
Strong acids are those that ionize entirely in solution or have a large concentration of the ion. Example-Sulfuric acid, Hydrochloric acid
Weak acids are acids that do not entirely ionize in solution or have a low concentration of the ion. Example-Oxalic acid, Acetic acid
Acetic acid has a methyl group linked to the Carboxylic acid, which has a positive inductive action and raises the electron density on the carbon of the carboxylic group, resulting in lowering its acidity.
Also, when it is dissolved in water it gives acetate and hydronium ions The equilibrium is moved to the right because the acetate ion is a stronger base than water. As a result of the decreasing concentration of hydronium ions, acetic acid becomes weaker.
Hence, it is not dissociated completely in water since it can give only one hydrogen rest three hydrogens are associated with methyl.