question about weak and strong alkali (identiflying)

Sodium hydroxide and potassium hydroxide are strong alkalis.
Ammonia is a weak alkali.

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Reasons:
Sodium hydroxide and potassium hydroxide are completely dissociated in water to give OH-(aq).
NaOH(s) + aq → Na+(aq) + OH-(aq)
KOH(s) + aq → K+(aq) + OH-(aq)

Ammonia is partly ionized in water to give OH-(aq).
NH3(aq) + H2O(l) ≒ NH4+(aq) + OH-(aq)