If you're talking about electricity, what does "DC" stand for?

In electricity, DC stands for direct current. Direct current is electric charge flowing in one direction, unlike alternating current, or AC, which periodically reverses direction.

A battery is a familiar source of DC power: its positive and negative terminals establish a polarity that drives current through a circuit. Solar panels also produce DC, and most electronic devices ultimately operate on DC even when they are plugged into an AC household supply. A power adapter or internal circuit converts the incoming electricity into the voltage the device needs.

“Direct” does not always mean perfectly constant. In technical use, DC can describe electricity with a fixed polarity even if its voltage or current fluctuates somewhat. A rectifier converts AC into DC, while an inverter performs the reverse conversion. This makes it possible to use DC batteries in systems designed to connect with AC power networks.

Thomas Edison promoted DC electricity for early lighting systems, but AC became dominant for long-distance distribution because transformers could efficiently raise and lower its voltage. High-voltage direct current later became valuable for long underwater cables and specialized power links.