発達:はったつ 、発展:はってん、、発育:はついく n3語彙
They all mean "development", but you have to choose the right word depending on what is the developing object.
- 発育: a human (from a baby to an adult), a pet
- 発展: a city (from a village to a large country), an organization (from a small workshop to a conglomerate), an event
- 発達: a skill, an organ (brains, muscles, extremities, etc)