回まわり階かい段だん

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Meanings

winder staircase

A staircase where the steps turn a corner without a landing, using wedge-shaped steps.

螺ら旋せん階かい段だん
螺旋階段 is a spiral staircase that curves continuously, while 回り階段 has a turn with wedge-shaped steps but no central pole.
折おり返かえし階かい段だん
折り返し階段 is a staircase with a landing where the direction reverses, unlike 回り階段 which turns without a landing.

Compound of 回り (まわり, 'turning') + 階段 (かいだん, 'staircase'). The variant 廻り階段 uses the character 廻, which also means 'to go around'.