Simplify the following text for a Grade 6 native English-speaking person.
Original: The watt ( ; symbol : W ) is a derived unit of power in the International System of Units ( SI ) , named after the Scottish engineer James Watt ( 1736 â `` 1819 ) .
Simplified: The watt ( symbol : W ) is the SI unit of power . It is named in honor of the physicist James Watt ( 1736 â `` 1819 ) .