expression, godan verb (-ru)
become a thing of the past
Used when something is no longer relevant, current, or in use; often implies obsolescence or being outdated.
スマートフォンの普及で、公衆電話は過去のものになった。
With the spread of smartphones, public telephones have become a thing of the past.
Standard kanji-kana mixed spelling.
Alternate kanji for もの; both are used.
Phrase composed of 過去 (past) + の (possessive particle) + もの (thing) + になる (to become).