Difference between Useless and Extraneous

USELESS vs EXTRANEOUS: ADJECTIVE

Not essential
Not pertinent to the matter under consideration
Not belonging to that in which it is contained; introduced from an outside source
Coming from the outside
Not constituting an essential or vital element or part.
Unrelated to the topic or matter at hand. : irrelevant.
Not belonging to, or dependent upon, a thing; without or beyond a thing; not essential or intrinsic; foreign.
Not essential or intrinsic

Having no use; being of no use; unserviceable; usable to no good end; answering no valuable purpose; not advancing the end proposed; unprofitable; ineffectual.
Synonyms Useless, Fruitless, Ineffectual, Unavailing, bootless, profitless, unprofitable, valueless, worthless, futile, abortive. Useless often implies that the cause of failure lies in the situation; as, it is useless to try to mend that clock. Useless is the only one of these words that may thus be applied by anticipation to what might be attempted. That which is fruitless, ineffectual, or unavailing actually fails, and from hindrances external to itself. Unavailing is more likely to be used the fruitless or ineffectual where the failure is through some one's unwillingness; as, unavailing prayers or petitions, ineffectual efforts, fruitless labors. Fruitless is stronger and more final than ineffectual or unavailing.

Introduced from an outside source
Synonyms See exterior.
Not belonging or proper to a thing; not intrinsic or essential, though attached; foreign: as, to separate gold from extraneous matter; extraneous ornaments or observances.
In music, not belonging to a standard scale or key; chromatic.

Cast off, Scrap, Waste, Unprofitable, Junked, Unavailing, Unserviceable, Discarded, Otiose, Inutile, Unhelpful, Unuseable, Ineffectual, Unusable, Futile

Needless, Unrelated, Vexatious, Useless, Unnecessary, Superfluous, Outside, Adulterating, Adulterant, Foreign, Impertinent, External, Immaterial, Extrinsic, Irrelevant

Cast off, Scrap, Waste, Unprofitable, Junked, Unavailing, Unserviceable, Discarded, Otiose, Inutile, Unhelpful, Unuseable, Ineffectual, Unusable, Futile

Exogenous, Needless, Unrelated, Vexatious, Useless, Unnecessary, Superfluous, Outside, Adulterating, Foreign, Impertinent, External, Immaterial, Extrinsic, Irrelevant

The principal, teachers and IT staff are useless.
It does not make you a useless idiot.
Otherwise, they risk being misunderstood and therefore useless.
TRIED CALLING MTNL CUSTOMER CARE BUT ASUSUAL USELESS.
How The Meta is Shifting; Most Useless Commander?
Program sandbags are useless without having the bodyweight!
Stop wasting your time with those useless methods.
Cut all the useless clubs, the unnecessary tables, the investments that are fun to be in but useless to the bottom line.
While the temptations to go in useless or worse than useless direction, certainly exists, there are amazing things on the internet.
If Christ was not raised, then all our preaching is useless, and your trust in God is useless.