Complicated means having many connected parts or steps that are difficult to understand or deal with. A complicated math problem might have multiple steps that all depend on each other, while a simple problem has just one or two operations. A complicated machine, like a car engine, has hundreds of parts working together, unlike a simple machine like a lever.

When something is complicated, you usually need to think carefully or learn more before you can understand or solve it. A complicated story might have many characters whose lives intersect in surprising ways. Complicated instructions might require you to read them several times before they make sense.

People sometimes confuse complicated with complex. While they're similar, complex often suggests something sophisticated or intricate that rewards careful study, while complicated sometimes hints that something is harder than it needs to be. A chess game is complex because it has elegant depth. A bureaucratic form might be needlessly complicated because someone made it confusing.

Things can also become complicated in a different sense when situations get messy or difficult to navigate. If you accidentally promise to attend two birthday parties on the same day, that situation has gotten complicated. When people say “it's complicated,” they often mean a situation has layers of difficulty that aren't easy to explain.