The bond angle in Ammonia is

In Ammonia, the central atom Nitrogen has three bond pairs and one lone pair of electrons with pyramidal geometry and bond angle as $107°{48}^1$ .  In this case Nitrogen atom undergoes ${\text{sp}}^{\text{3}}$  hybridization.

In Ammonia central atom ‘N’ undergoes  $s{p}^3$  hybridization means bond angle is  $109°28\text{'}$  but it changes from  $109°28\text{'}$  to $107°48\text{'}$  due to lone pair and bond pair repulsion on ‘N’ in  $N{H}_3$ .