why this sentence has this grammatical structure? 話し手も相手も共通に知っている場合


The phrase "話し手も相手も共通に知っている場合" was translated in this board as "When both the
speaker and listener know the subject"

I dont understand 2 things about this sentence. What's the use of ni in this
phrase. It doesnt seem to match with any of the uses of "ni" I know. Isnt
話し手も相手も共通 the topic of the sentence and should be marked with "は". And why
"the subject" isnt before the 知っている verb and it isnt marked with を ?




I understand "共通に" can be correspoond to "both."

"話し手も相手も共通に話題を知っている場合" = "When（場合） both（共通に） the speaker（話し手） and（も）
listener（相手） know（知っている） the subject（話題(を)）"

"話し手も相手も共通に知っている場合" = "When both the speaker and listener know the subject"

"話し手も相手も知っている場合" = "When the speaker and listener know the subject"

The nuance of difference is quite week.




I understand "共通に" can be correspoond to "both."

"話し手も相手も共通に話題を知っている場合" = "When（場合） both（共通に） the speaker（話し手） and（も）
listener（相手） know（知っている） the subject（話題(を)）"

"話し手も相手も共通に知っている場合" = "When both the speaker and listener know the subject"

"話し手も相手も知っている場合" = "When the speaker and listener know the subject"

The nuance of difference is quite week.

