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

He is the unsung hero of the team.

I hurried down the lower two steps.

He is good at programming, so he started a new project as if he were setting sail on his strong point.

Please refrain from going out because a typhoon is approaching.

His new car is a Mustang.

Her new dress is super cool, isn't it?

He is preparing the props to use on stage.

Carrying the stage props of the theater company is a tough job.

Grieg is a famous composer from Norway.