GRAMMAR DETAIL

とする

to designate as · to assume that

Designates a person or thing for a role or treats a statement as an assumption for discussion.

Examples

この部屋を会議室とする。

This room will be designated as the conference room.

費用は一万円だとする。

Let us assume that the cost is ten thousand yen.

Structure: Use とする to designate something or to take a plain-form statement as an assumption for discussion.
Basic usage: 費用は一万円だとする。 places the discussion under the assumption that the cost is ten thousand yen.

Designating an object and assuming a statement
- この部屋を会議室とする assigns the room a role. この部屋は会議室だとする assumes the statement that it is a conference room, giving を and clause-final だ different roles.
An assumption and a factual report
- 費用は一万円だとする supplies a starting point for calculation or discussion. Distinguish it from the report of a settled cost in 費用は一万円に決まった.