That information is completely unnecessary.

He thinks that war is a necessary evil.

Avogadro's constant is a very important constant in physics.

Differential geometry is a field of mathematics that studies geometric objects such as curves and surfaces using differential and integral calculus.

The Planck's constant is one of the fundamental constants in physics.

This recipe requires a certain amount of ingredients.

He makes it a point to read a certain number of books every month.

What is the constant term of this equation?

Understanding chemical equations is difficult.

He is good at solving algebraic equations.