noun, used as a suffix, noun which may take the genitive case particle 'no'
stopped in the midst of; half-
Attaches to the -masu stem of a verb to mean that the action was started but not completed. Often used with verbs like 読む (→ 読みさし), 食べる (→ 食べさし), or 書く (→ 書きさし). The resulting noun can be used with の to modify another noun.
机の上に読みさしの本が置いてある。
A half-read book is on the desk.
彼は食べさしのパンをテーブルに置いた。
He put the half-eaten bread on the table.
Derived from the -masu stem of the verb 止す (さす, 'to stop/cease'), used as a suffix to indicate an action that was stopped partway.