Observing variable stars is an important part of astronomy.

He is editing the article.

Her cheeks turned red.

Affine transformation is an important concept in geometry.

Her fluttering movements were just like a butterfly.

This software has a function to convert images into text.

I need to convert this file to PDF.

In mathematics, a variable forms part of an equation.

Polarized sunglasses are used to reduce glare.

There is a clear bias in his reporting.