Patrick Newman (patorick002@gmail.com). Revised in January 2024 from a post from 2014 from my old blog.
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 starting to leak out into the real world. The most recent that comes to mind is umami, "savory," which has provided the name of at least one restaurant and now autocompletes when I type it. I've seen toys on children's television being described as kawaii (cute), without any explanation necessary. The term cosplay (costume play) seems to have earned promotion out of Otaku territory in and into the mainstream. More recently, I assume Marie Kondo has injected some new vocabulary into the English vernacular, though I'll admit I'm not familiar with her work enough to know what those might be.
I live in America, but I speak and read Japanese every day. 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 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"). Genki also convenys a little more spirit; a very active, cheerful person can be described as "genki ippai" ("full of energy").
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," in a way I don't think we have an English equivalent for. But you can also use it in other ways, too. 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 equivalents 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 know that person or thing that always comes through for you? That person is sasuga. Shohei Ohtani just hit another home run? "Sasuga, Ohtani." The place was open on the holiday and had exactly the thing you needed? "Sasuga, that shop." For me, sasuga conveys a combination of reliability and excellence. The literal dictionary translation of sasuga is something like "certain", but English ways of expressing certainty. I don't know if English has another word that really captures the specific nuance of sasuga.
Yappari: Yappari means something like "as it turns out" or "after all," but it's more like what you feared or expected turned out to be true. It can be an expression of joy or resignation, like "I knew you could do it!" or like "just as I suspected". "The game was close, but we pulled through in the end, yappari." "Yappari, my car needs its brakes repaired."
In Japanese, yappari can be used in response as well, in the same way. Partner A: "The mechanic said the brakes need to be replaced." Partner B: "Yappari." Kid: "I was worried about my test, but I got an A." Parent: "Yappari."
Or, it can be a re-affirmation: "I tried the new cafe, but yappari the other one is still the best."