Body, soul, and reason, are the three constituent parts of a man.
Oxygen and hydrogen are the constituent parts of water.
CONSTITUENT, n.
1. He or that which sets, fixes or forms; he or that which constitutes or composes.
Their first composure and origination requires a higher and nobler constituent than chance.
2. That which constitutes or composes, as a part, or an essential part.
The lymph in those glands is a necessary constituent of the aliment.
3. One who appoints or elects another to an office or employment.