usefulness

Concise Oxford English Dictionary © 2008 Oxford University Press:
useful/ˈjuːsfl/

▶adjective

• 1 able to be used for a practical purpose or in several ways.

• 2 Brit. informal very able or competent.

– phrases
make oneself useful do something that is of some value or benefit.

– derivatives
usefully adverb,
usefulness noun.