Answer:
By myself, I'm practically nothing. Worthless as a leader, but when I follow a group, their strength increases tenfold. What am I?
I can fall off a building and live but in water I will die.
What runs but never walks has a mouth but never talks has a head but never weeps has a bed but never sleeps?
I have a hundred legs but cannot stand. I have a long neck but no head. I cannot see and I help keep your house neat and tidy.
The letter S is added to pluralise most words in the English language. eg. Letter to Letters Word to Words and Language to Languages. But I am a word that is pluralised with the addition of the letter C.
No matter how little or how much you use me, you change me every month.