通す【とおす】

The verb とおす通す (とおす), when attached to the ます-stem of another verb, functions as a compound verb suffix meaning "to do something all the way through to the end" or "to keep doing something without stopping." It emphasizes persistence, perseverance, or completion of an action from beginning to end.

Structure

V[ます stem] + 通す

• はしる走る → 走り + 通す → 走り通す (to run the whole way through)
• よむ読む → 読み + 通す → 読み通す (to read all the way through)
• やる → やり + 通す → やり通す (to see something through to the end)

Expressing perseverance

This pattern highlights that the speaker (or subject) did not give up or stop partway through. It often carries a nuance of effort or determination.

Expressing continuity without interruption

通す can also emphasize that an action continued without pause or interruption over a period of time.

The noun form ～通し (とおし) is also common, especially in expressions like たちどおし立ち通し (standing the whole time) and あるきとおし歩き通し (walking non-stop).

Sticking to a belief or position

When used with verbs related to opinions or principles, 通す conveys the idea of holding firm or insisting to the very end.

Conjugation

Since 通す is a godan (五段) verb, it conjugates normally: やり通す → やり通した (past) → やり通さない (negative) → やり通します (polite).