Thanks predominantly to the Internet and maybe helped along by the spread of Otaku culture, a few Japanese words are finding their way into the English vernacular. While I first noticed some of these words online years ago, a few are making their way into the real world. The latest seems to be umami (savory). I'm seeing that word used on food websites, and a few blocks away from my home in the Bay Area, you'll find an Umami Burger. I've also seen toys on children's television being described as kawaii (cute), without much explanation necessary. The Toyota Way introduced the business community to terms like kaizen (continuous improvement) and muda (waste). And the term cosplay (costume play) seems to be sneaking out of Otaku-land and into the mainstream.
I live in America, but I speak and read Japanese every day, and over time I've developed a reliance on a couple of Japanese words that I can't quite translate into English. So if the fantastic flexibility of the English language can handle a few more imports, I'd like to suggest the following:
Genki: I don't have any data on this, but I think genki might be the most heavily used adjective in the Japanese language. It translates literally to "energetic", but it's used with a little more flexibility, to describe any level of energy. Among it's uses, it can be a generic greeting - "genki desuka" ("How are you?" "Are you genki?"); a positive response - "genki desu" ("I'm good"/"I'm genki"); a negative one - "genki janai" ("I'm not good", "I'm sick").
In English I find myself wanting to say, "wow, that kid is genki." Or maybe, "I'm feeling genki today. Let's go for a run." Sure, there are English words that work just fine in either situation, but I don't think they are quite as fun.
Sukkiri: The most literal translation for sukkiri is probably "refreshed". After stepping out of a bath or shower, a Japanese person might say, "ahh, sukkiri". But you can also use it in other ways. I knew a guy who had a shaggy head of hair that he would get cut once or twice a year. Every time he cut his hair, it would be trim and straight, and the only think I could think to say was "sukkiri". You can feel sukkiri after cleaning something up.
Hakkiri: I guess the closest translation for hakkiri would be direct, straight or clear, but for me it conveys those concepts a little more succinctly. The Japanese might say "kanojo wa suki kirai hakkiri suru ne", which translates to "she's very clear about what she likes and dislikes". Maybe it's just me, but to say something like, "she's hakkiri about what she likes and dislikes," sounds more definite, as if the woman in this sentence has taken a butcher's knife and sliced a thin, precise line between what she likes and doesn't like. Hakkiri.
Sasuga: You that person or thing that always comes through for you? Maybe you just read another great article on NPB Tracker. In Japanese, you might say "sasuga, NPB Tracker." Sasuga. We can always count on you. Actually, you probably wouldn't need to say that much lately.
More literally sasuga translates to something like "certain", but English has that. I don't know if English has another word that really captures the other usage.
Yappari: Yappari means something like "as it turns out" or "after all". Depending on the context, it can be somewhat negative, like "just as I suspected". "Yappari, my car needs its brakes repaired." Or it can be something of an affirmation. "The mechanic said the brakes need to be replaced." "Yappari." Or even a re-affirmation: "I tried the new cafe, but yappari the old one is still the best."
I don't really think I'm doing the range of these words justice; it's probably not possible to in a few brief paragraphs. If anyone happen to have other/better examples to add to the list, please feel free to do so.
To be continued, if I can think of a more profound conclusion for this.