What does this at sign mean?

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

The bass clef is one of the basic elements of music.

Reading clefs is difficult.

Can you tell me the phonetic symbol of this word?

By learning phonetic symbols, accurate pronunciation becomes possible.

They appear to be antagonistic on the surface, but in reality, they are seemingly not part of the same group.

He is good at reading the treble clef.

The treble clef is often used in musical scores.

The International Phonetic Alphabet is an essential tool for linguistic research.