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.

I stabbed the needle for the injection.

Three days ago, I went to Tokyo.

He was feeling loneliness.

He provided a detailed explanation to elucidate the issue.

This job is suitable for him.

World War I was a large-scale war that lasted from 1914 to 1918.

He was anxious about starting a new business, but I encouraged him by saying, 'Even a journey of a thousand miles begins with a single step.'