In mathematics, a perfect number refers to a number where the sum of its divisors, excluding the number itself, equals the number.

The water conveyance system in this area is very efficient.

This pipe is used to convey water from the river to the town.

He is known as the highest leader of the organization.

He is an expert in brooding, always looking for the best ways to maintain the health of chickens.

He built a coop to brood chickens.

He is good at remembering consecutive numbers.

I have five pencils.

Chamaeleon is one of the constellations in the southern hemisphere.

Heavy hydrogen is one of the isotopes of hydrogen.