～（さ）す
short causative, casual make / let
～（さ）す is a compact variant of the causative せる／させる: 行かす = 行かせる “make/let (someone) go”, 食べさす = 食べさせる “make/let (someone) eat”. The meaning is the same: the subject makes or lets someone act.
It is colloquial, especially common in western Japan, and in writing it can sound literary. You will hear it constantly in casual speech.
1. Casual “make/let someone do”
It works exactly like the standard causative: the person made to act takes に, or を with intransitive verbs.
弟を買い物に行かした。
“I made my little brother go shopping.”
- 弟（おとうと）= younger brother
- を = marks the person made to act
- 買い物（かいもの）= shopping
- に = purpose marker (to/for)
- 行かした（いかした）= made (him) go
2. Casual requests with ～して
Because ～す conjugates like a godan verb, its て-form is ～して, which shows up in casual requests for permission.
ちょっと休まして。
“Let me rest a sec.”
- ちょっと = a little / a sec
- 休まして（やすまして）= let (me) rest (casual request)
How to form it
Godan (u-) verbs: change the final u-sound to its a-row sound and add す. Ichidan (ru-) verbs: drop る and add さす. Irregular verbs: する → さす, 来る → 来さす（こさす）.
- 行く（いく）= to go → 行かす（いかす）= make/let go
- 話す（はなす）= to speak → 話さす（はなさす）= make/let speak
- 飲む（のむ）= to drink → 飲ます（のます）= make/let drink
- 食べる（たべる）= to eat → 食べさす（たべさす）= make/let eat
- する = to do → さす = make/let do
- 来る（くる）= to come → 来さす（こさす）= make/let come
Key idea
～（さ）す is the causative in a shorter, more casual coat. It has the same “make/let” meaning as せる／させる, but it behaves like a godan verb.
Built on the same stem
Updated .