"Sûi-ti̍t" pán-pún chi-kan bô-kāng--ê tē-hng

[[File:Perpendicular-coloured.svg|right|250px|thumb|Sûi-ti̍t]]

'''Sûi-ti̍t''' (垂直; {{lang|en|''perpendicular''}}) sī chi̍t ê [[kí-hô-ha̍k]] ê su̍t-gú. Tī [[Euclid kí-hô|pêng-bīn kí-hô]] tiong, nā ū chi̍t tiâu [[ti̍t-soàⁿ]] kap lēng-gōa chi̍t tiâu ti̍t-soàⁿ sio-kau, nn̄g ê hō͘-siong kīn-oá ê [[kak-tō͘]] nā sio-siâng, chit nn̄g tiâu ti̍t-soàⁿ tiō hō-chò sûi-ti̍t; ah chit-ê kak-tō͘ tiō hō-chò [[ti̍t-kak]].

[[Category:Hong-hiòng]]