三角函数[sankakukansuu] trigonometrical function
投函[toukan] mailing
函れる[ireru] to put in
函蓋[kangai] box and cover
函渠[kankyo] drain with an oblong cross-section

函人[kanjin] armorer
函嶺[kanrei] the Hakone Mountains
函数[kansuu] function (e.g. math, programming, programing)
逆函数[gyakukansuu] inverse function