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.

He explained the importance of studying while young, saying 'If you do not study when you are young, it will be difficult to learn when you are old.'

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.

The 24-cell is one of the geometric shapes in four dimensions.

The 120-cell is one of the regular polytopes in four dimensions.