Ha̍p

Ha̍p (合) ê sò͘-ha̍k hû-hō sī Σ (sigma). Chit-ê hû-hō siōng-chá sī iû sò͘-ha̍k-ka Leonhard Euler tāi-seng khai-sí sú-iōng. Σ sī Hi-lia̍p-bûn "σογμαρω" ê jī-thâu, kî-tiong "σογμαρω" tāi-piáu tio̍h "cheng-ka" ê ì-sù; Σ chiū sī σ ê tōa-siá. Ha̍p ê tōng-chok hō-chò kiû-ha̍p (求合) ia̍h-sī ka-chóng (加總).

${\displaystyle \sum _{i\mathop {=} m}^{n}a_{i}=a_{m}+a_{m+1}+a_{m+2}+\cdots +a_{n-1}+a_{n}}$