(auxiliary verb, Ichidan verb)
(1) (せる is for 五段 verbs, させる for 一段; follows the imperfective form of and verbs; senses 1-3 of せる are sometimes abbreviated as 〜す) auxiliary verb indicating the causative (noun or participle which takes the aux. verb suru) (Godan verb (not completely classified))
(2) (usu. as 〜(さ)せてもらう, 〜(さ)せていただく, etc.) auxiliary verb indicating that one has been granted the permission to do something (humble (kenjougo) language)
(3) auxiliary verb used to make verbs more "active"
(4) (as 〜(さ)せられる, 〜あら(さ)せられる, 〜(さ)せ給う, etc.) auxiliary verb used as an extreme honorific for others' actions (honorific or respectful (sonkeigo) language)