「複雑 (fukuzatsu)」 means complex or complicated. It describes something with many parts that is difficult to understand or solve, like a complicated problem or a complex machine. Example: この問題は複雑です (Kono mondai wa fukuzatsu desu - This problem is complex).

「複雑」は、物事が入り組んでいて理解や解決が難しい様子を表します。「複雑な問題」のように使います。