複雑 (fukuzatsu) means “complex” | MotiTan Japanese Dictionary

More examples

話が複雑になったので、結論を出せません。hanashi ga fuku zatsu ni na tta no de ketsu ron o da se ma se n

The discussion became complicated, so we cannot reach a conclusion.

Refers to a structure or situation that contains many connected elements rather than a single simple part.

煩雑hanzatsu: Describes a task or process with many details that make it difficult to handle.

物事の要素や関係が多く入り組み、簡単には整理できないさま。mono goto no yō so ya kan kei ga ō ku i ri ku mi kan tan ni wa sei ri de ki na i sa ma

複 (fuku, "multiple") and 雑 (zatsu, "mixed") combine in 複雑 (fukuzatsu) to express a mixture of multiple elements.

English speakers use complex for systems, problems, and ideas with many interacting parts, so it is common in both daily and formal conversation.