Strong Electrolytes: These are the substances which when dissolved in water (solvent) dissociates completely into ions.
ex- `NaCl ⇋ Na^(+)+Cl^(-)`

Weak Electrolytes:These are the substances which when dissolved in water (solvent) dissociates partially into ions.
ex- `CH_3COOH ⇋ CH_3COO^(-)+H^(+)`

Some electrolytes, e.g., mineral acids such as `H_2SO_4, HCl` and `HNO_3`, alkalis such as `NaOH` and `KOH` and all salts have a very high degree of ionization (`alpha` nearly equal to `1`) at all reasonable concentrations. They are known as strong electrolytes. The number of ions in solutions of strong electrolytes is large and thus such solutions have high conductance.

Some electrolytes, e.g., organic acids such as acetic acid, propionic acid. etc., and bases like ammonium hydroxide have a low degree of ionization in solution. They are called weak electrolytes. The number of ions in solutions of weak electrolytes is quite small and thus such solutions have low conductance.

A solvent which has a high dielectric constant weakens the attractive force between the cations and anions. Hence a solvent of high dielectric constant favours the dissociation of the electrolyte. Likewise a solvent which can solvate the ions readily, and can release energy by solvation, favours the dissociation of the electrolyte. Thus, the dissociation of acids in water is favoured by the hydration of the hydrogen ions to form hydronium ions. The enthalpy of hydration of the proton has a very high value.

For some electrolytes, degree of dissociation increases with dilution as explained by Ostwald's dilution law (will beexplained later).

Increase of temperature generally increases ionization.