You connect an ammeter to a circuit. The ammeter shows you that there are 5 amperes of __________ in the circuit. What one word completes the sentence?

The one word that completes the sentence is "current."

An ammeter is a device used to measure the electric current flowing through a circuit. When you connect an ammeter in series with a circuit and it indicates a reading of 5 amperes, it means that there is a flow of electric charge (current) of 5 amperes measured at that point in the circuit. The term "current" specifically refers to the rate at which electric charge flows, and it is commonly denoted by the symbol $I$. In this case, the reading tells you how much charge passes through a point in the circuit each second, highlighting the importance of electric current in understanding and analyzing electrical circuits.