試行 and 試行錯誤: A trial and a process of trial and error
Compare repeated trials or a limited trial implementation with the process that produced fluffy bread or a new procedure. The distinction is not simply one attempt versus many.
A trial can involve several attempts
試行 means a trial or experimental implementation. 「何度か試行して最も効率のよい手順を選んだ。」 says several trials were made before the most efficient procedure was chosen.
「新しい制度は一部の地域で試行される。」 says a new system will be tried in some regions. Preserve 一部の地域 and the nonpast form; do not turn this into a completed, nationwide, full implementation.
A method found through trial and error
試行錯誤 means trial and error. 「何度も試行錯誤を重ね、ようやくパンがふっくら焼けた。」 states that repeated trial and error finally produced fluffy bread.
「新しい作業手順は現場での試行錯誤から生まれた。」 says a new procedure emerged from trial and error in the field. The bread’s result and the procedure’s origin are the respective stated outcomes.
Compare the focus of the process
試行 can include several attempts, as 何度か shows. Treating 試行 as exactly one attempt and 試行錯誤 as multiple attempts would misread the first example.
試行 emphasizes trying something experimentally, while 試行錯誤 emphasizes working toward a method through attempts and adjustments. The examples do not say that every trial fails or that every success must be preceded by repeated failure.
Does 何度か試行して support the claim that 試行 always means trying only once?
Show the answer and why
No. This example states that several trials preceded the selection of a procedure. Compare experimental execution with a process of finding a method, rather than distinguishing the words solely by the number of attempts.