Ruble is the American spelling of the word for Russia’s money. British writers usually write rouble. Same coin, same word — only the letters change with the dictionary. One ruble splits into 100 smaller coins called kopecks. People also use ruble for the money of a few other places that once sat in the old Soviet world; Belarus is the one you will hear most, though actually Belarus often writes it rubel, a close cousin rather than a typing error. In everyday English you meet it in the news: prices, oil, sanctions, exchange rates. It is a plain, neutral word, nothing slangy. It has no extra life as a verb or a joke in ordinary speech. The trap is the lookalike rubble, which is broken stone after a building falls. They are not related.