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

A lower triangular matrix is a matrix where all the elements below the main diagonal are zero.

My boat is equipped with the latest fishfinder.

She is conducting research on the world's oldest profession.

My father is an ichthyologist and has a deep knowledge about marine life.

He is interested in ichthyological research.

This area is rich in green tuff.

This area is rich in green tuff, forming a distinctive landscape.

Understanding the rules of 'Ha-gyou tenko' is difficult.

As soon as he arrived, he said 'I just got here.'