Did you hear his voice?

I work in the marketing division.

He was deeply grieving the death of his family.

His performance is generally good.

He followed the footprints left on the snow.

He was appointed as the chief executive officer of the company.

By regularly checking the key performance indicators, you can understand the performance of the company and devise improvement measures.

Functional analysis is a branch of mathematics that studies the properties of functions in infinite-dimensional spaces.

The Mesolithic is the era between the Paleolithic and the Neolithic.

The Riemann sum is a method for approximately calculating the integral of a function.