This text is organized using section signs.

Semiotics is the study of signs and symbols used in society and culture.

What does this at sign mean?

The Schläfli symbol is a part of geometry, used to represent the shape of polyhedra.

This reaction occurs through a chemical process.

He is an excellent chemist who made many discoveries.

He is an expert in petrochemistry.

It's difficult to decipher this chemical equation.

Understanding chemical equations is difficult.

He is an expert in chemical analysis.