noun
standard language; standard variety
Refers to the codified standard form of a language used in official, educational, and media contexts. In Japanese contexts, it often specifically means the Tokyo-based standard Japanese.
学校では標準語を使うように指導される。
At school, students are instructed to use standard language.
noun
standard Japanese
When the context is clearly about Japanese, 標準語 is understood as the Tokyo-based standard Japanese, as opposed to regional dialects.
彼は関西弁ではなく標準語で話した。
He spoke in standard Japanese, not Kansai dialect.
方言 means dialect; 標準語 is the standard language contrasted with regional dialects.
Compound of 標準 (standard) + 語 (language). The term became common in the Meiji period with the establishment of a national standard language.