percent

Percent means one part in every hundred. Ten percent of a hundred pounds is ten pounds.

The word comes from Latin per centum, by the hundred, and British English still often writes it as two words or as per cent. The symbol is the one everybody knows. Keep the noun percentage separate, since you say twenty percent but a small percentage, never a small percent. And beware the trap of percentage points, because a rise from four percent to six is two points but a fifty percent increase.