A tesseract is a four-dimensional geometric shape.

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

He was neglecting his work.

He had his coins exchanged.

His name is Tai, which means peace.

The police apprehended the criminal.

He is the leader of that team.

A skew-symmetric matrix has the characteristic that its transpose matrix is the inverse of the original matrix.

A diagonal matrix is a matrix in which all elements outside the main diagonal are zero.

The diagonal elements of this matrix are all 1.