割り

Conjunctive or noun form of the verb 割(わ)る (waru, “divide; cut”).

割(わ)り • (wari) 

1. ratio, proportion
2. a one-tenth portion

   ２(に)割(わ)り引(び)き ― ni wari biki ― twenty percent discount

3. (of drinks, with preceding noun) mixed with or diluted with

   水(みず)割(わ)り ― mizu wari ― mixed with water

   • 2019 September 28, “Fuyu ni au! Oyu-wari to aishō no ii shōchū no osusume meigara rokusen [Made for winter! Six selections of shochu that are good with hot water]”, in Bakkasu‎^[1], archived from the original on 24 September 2020:

     香(かお)りがふんわり立(た)ち、身体(しんたい)を温(あたた)めてくれるお湯(ゆ)割(わ)りは、寒(さむ)い時期(じき)にこそ呑(の)みたいもの。

     Kaori ga funwari tachi, shintai o atatamete-kureru oyu-wari wa, samui jiki ni koso nomitai mono.

     With a gentle aroma to warm my body, [shochu] mixed with hot water is what I want to drink in cold weather.

• Often written 割, especially for the "ratio" sense.