He is a world-famous mathematician.

He was my travel companion.

The debtor has an obligation to repay his debt.

The duty of a taxpayer is to pay taxes accurately.

He was known as a forger.

He is recognized as a strong competitor.

Communication with the interlocutor is very important.

As an interlocutor, he always provides a new perspective.

He is suspected to be the ringleader of the incident.

He is a complete outsider to this issue.