In a language as different from English as Japanese is, naturally there are situations where vocabulary words from one language don’t match neatly with words from the other. In Japanese the words for “lock” and “key” are both covered by the word kagi, which seems confusing to me, though they have no problem with it. Similarly the word futon describes a traditional sleeping mat as well as the blanket that goes over it. The words for “lightning” and “thunder” are both kaminari, another confusing concept since we have separate words in English — Japanese might differentiate them with onomatopoeia, using pika! for lightning and goro-goro for thunder. Then there are linguistic concepts covered by one word in English which are split into two in Japanese, like “cold,” which is tsumetai when describing coldness to the touch but samui for coldness in the air. No matter what situation a freezing foreigner finds himself in, he will accidentally use the wrong word first…
Both thunder and lightning are kaminari in Japanese.