If you describe an action as senseless, you think it is wrong
because it has no purpose and produces no benefit.
If you feel hopeless, you feel very unhappy because there seems to be no
possibility of a better situation or success.
Countless means very
many.
If you describe something such as furniture, clothing, or the way
that a house is decorated as tasteless, you consider it to be vulgar
and unattractive.
If the sky is cloudless, there are no clouds in
it.
Cheerless places or weather are dull and depressing.
Something
that is effortless is done easily and well.
A sleepless night is
one during which you do not sleep.
If something is useless, you
cannot use it.
Something that is worthless is of no real value or use.