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spoken language; colloquial expression
論文では話し言葉を使わないように注意した。
I was careful not to use colloquial expressions in my thesis.
話し言葉は省略が多い。
Spoken language has many abbreviations.
外国語の話し言葉は文法書から学ぶのが難しい。
It is difficult to learn spoken forms of a foreign language from grammar books.