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電車で小っちゃい子が「なんで "北海道は小っさいどう" は…」
→ “On the train, a little kid said, 'Why is Hokkaido so small?' and then...”
電車 densha = train (noun)
で de = by / on (location particle indicating means of transport)
小っちゃい chippai = small / tiny (colloquial adjective)
小 ko = small
っちゃ ccha = diminutive suffix for cuteness
い i = adjective ending
子 ko = child (noun)
が ga = subject marker particle
「 = opening quotation mark
なんで nande = why (informal interrogative)
" = closing quotation mark (English style)
北海道 hokkaidō¹ = Hokkaido (proper noun, region in Japan)
は wa = topic marker particle
小っさい chissai = small / little (colloquial adjective)
小 ko = small
っ tsu = geminate consonant (lengthens previous sound)
さい sai = size / extent
どう dō¹ = how / what (onomatopoeic/interjection used here to mimic childlike speech)
" = closing quotation mark (English style)
は wa = topic marker particle (repeated for emphasis or contrast)
…」 = ellipsis indicating trailing off or suspense