* ジョーカー (Jōkā): This is the most common and straightforward translation, a direct loanword from English. It's understood universally and works well in most contexts, especially when referring to the playing card.
* 道化師 (dōkeshi): This means "clown" or "buffoon." This is a good choice if you're referring to a joker as a comedic character, especially one who's mischievous or foolish.
* 悪役 (akuyaku): This means "villain" or "bad guy." This is appropriate if the joker is depicted as an antagonist or a malicious character, like the Batman villain.
* いたずら者 (itazura-mono): This translates to "prankster" or "mischief-maker." This is suitable if the joker's actions are playful and mischievous, rather than malicious.
Therefore, the best translation depends on the specific meaning you want to convey. For a playing card, ジョーカー (Jōkā) is best. For a character, consider the character's nature and choose accordingly.