In Washington DC, the subway is usually called "Metro", and the bus is called "metrobus". If you want to take public transportation, just looking for a tall brown columns with a large "M". People usually do not say "subway", which in fact is a name of American restaurant that sells sandwiches and salad.

In fact, the public transport in Washington DC is much worse than Beijing, China. The reason might be the Americans like to drive their own cars. First of all, the metro fare is quite expensive in DC. It depends on when and how far you travel, The basic price is about 2 dollars, and you need to buy farecard using farecard machines. This is different from Beijing, where 2 yuan could take you everywhere. 

The basic price of Metro is about 2 dollars. The distance between the place where I am living and the place where I am working will cost me 4 dollars at peak time. Fortunately, I usually came home at off-peak time. It is just 2.15 dollars. So I will spend at least over 4 dollars to take metro one day. Another disgusted thing is that you have to calculate that how much you need to pay each time, and you will get many small change. Fortunately, you could buy SmarTrip card at every CVS supermarket, and deposit your money in the card and swipe your card when you get in and out of the Metrorail. SmartTrip is also available for Metrobus.

Metrobus is quite inconvenient. The next but usually come in half a hour, only available at peak time, additionally, it is not in service on weekends and holidays (some works). But there are also some good news. The bus usually come on time, so you can schedule you time. Another good news is if you transfer from the metrorail to the metrobus in half a hour, you can save money.