The term "waifu" is a word that is used prevalently in the Manga/Cartoon, and Video-game fandoms. The origin of the word comes from the katakana word for wife; ワイフ However, Japanese-speakers will never use that word. The real word for wife is 妻 (tsuma/sai). "Waifu" is used to refer to a fictional girl or woman (usually in Anime, Manga, or video-games) that you have sexual attraction to, and you would even marry. Remember; "ワイフ waifu" and "妻 tsuma" are completely different. Waifu is a joke word that Anime fans call fictional female characters that they love and would marry if they were real. Your tsuma is your real wife. That is the real Japanese word for wife.