useful

is whatever lets the body be affected, and affect other bodies, in more ways; whatever narrows its range does harm.

Recast in definition form from: “Whatsoever disposes the human body, so as to render it capable of being affected in an increased number of ways, or of affecting external bodies in an increased number of ways, is useful to man; and is so, in proportion as the body is thereby rendered more capable of being affected or affecting other bodies in an increased number of …”

useful, n.Definitions

useful