傘
かさ
kasa
= umbrella
傘 (kasa) is one of those kanji that draws exactly what it means: look closely and you can see a canopy stretched over four little legs standing underneath it, like people sheltering together from the rain.
Kasa is the general word for umbrella, but the verb that goes with it trips up a lot of learners: you don’t “open” an umbrella in Japanese, you sasu it — kasa o sasu (to put up/use an umbrella) is the set phrase, and it’s the one native speakers actually reach for. Kasa also grows into a whole family of related words once you attach a prefix: higasa is a parasol for blocking sun rather than rain, oritatami-gasa is a folding umbrella small enough for a bag, and amagasa specifically emphasizes a rain umbrella (as opposed to a sun one). The vinyl kind everyone in Tokyo seems to be carrying has its own name too: binīru-gasa.
Notice how kasa becomes -gasa in almost every compound above — that’s rendaku, the sound change where a word’s first consonant voices (k→g) when it’s the second half of a compound. It’s not random; once you know to expect it, words like higasa and amagasa stop looking like separate vocabulary and start looking like the same word wearing different hats. The other thing to lock in early is the collocation kasa o sasu — learners often default to akeru (to open) by analogy with doors or boxes, but that sounds off to native ears. Also useful for small talk: kasa wo motte itta hou ga ii (“you’d better take an umbrella”) is the kind of line you’ll hear from a coworker or host checking the forecast before you head out.
Everyday use
コンビニでビニール傘を買った。
Konbini de binīru-gasa wo katta.
I bought a clear vinyl umbrella at the convenience store.
Casual / Social Media
また電車に傘忘れた…もう何本目？
Mata densha ni kasa wasureta… mō nanbon-me?
I left my umbrella on the train again… how many is that now?
Formal / Cultural context
岐阜の工房で和傘の職人技を見た。
Gifu no kōbō de wagasa no shokunin-waza wo mita.
I watched a craftsman’s skill with traditional paper umbrellas at a workshop in Gifu.
The clear plastic binīru-gasa is practically a Japanese invention story: developed for mass production in the 1950s-60s and now sold by the tens of millions every rainy season, it’s cheap enough (often under 500 yen from a convenience store) that people buy one on the spot when a sudden shower hits and think nothing of leaving it behind on a train or in a stand outside a shop. That disposability has real downstream effects — lost-and-found bins overflowing with identical umbrellas, and a wave of umbrella-sharing services that sprang up specifically to cut down on the waste.
Set against that convenience culture is wagasa, the traditional Japanese paper umbrella made from bamboo ribs, hand-lacquered washi paper, and oil for waterproofing. Producing one is slow, specialized work, and the number of workshops still doing it by hand has shrunk to a handful of regions, Gifu and Kyoto among the most known. You’ll rarely see a wagasa used against actual rain today — instead it turns up as a prop in traditional dance, a fixture of the tea ceremony garden, and an image rakugo storytellers can conjure with a single gesture of an open fan.