In organic chemistry, the concept of cis-trans isomers is important.

The study of filterable pathogens is an important part of virology.

In organic chemistry, the concept of conformational isomers is very important.

A tesseract is a four-dimensional geometric shape.

A 5-cell is a simple convex polytope in four dimensions.

I read a eulogy praising his achievements.

I have started learning Traditional Chinese.

I am learning Simplified Chinese.

The 16-cell is one of the convex regular polytopes in four dimensions.

The 600-cell is one of the regular polytopes in four dimensions.