Ammonia is a base but doesn’t contain any hydroxyl group because it forms OH- ions when it is added to water.In water, ammonia forms\xa0ammonium hydroxide. While adding water, ammonia\xa0ionises\xa0for forming the ions of ammonium and hydroxide ions. In water, ammonia accepts the protons which are provided by dissociation of water. Water in this case which acts as an ‘acid’ and since ammonia accepts these protons, which it acts as a ‘base’.
Because it shows its basic nature is observed when dissolved in water.NH3+H2O=NH4OHHere hydroxide ions are formed i.e. responsible for basic nature of NH3.