～と同時に

About

The 「と同時どうじに」 pattern is a combination of the と particle, the noun 同時どうじ ("simultaneous; concurrent; same time") and the に particle. ～と同時に is used to express "at the same time; simultaneously".

～と同時どうじに has two main usages:

① Two actions happen at the same time

E.g. 教室きょうしつに入はいると同時どうじにチャイムが鳴なった。 "As I entered the classroom, the bell rang."

For usage ①, と同時どうじに can attach to casual form verbs, and nouns.

For usage ①, と同時どうじに tends to be used with instantaneous/quick actions.

② Two aspects are true simultaneously

E.g. これはスーツケースとして使つかえると同時どうじに、椅子いすにもなる。 "While you can use this as a suitcase, it can also become a chair."

For usage ②, と同時どうじに can attach to casual form verbs/い-adjectives, and to nouns/な-adjectives using である.

Summary

• 

  ～と同時に is used to express "at the same time; simultaneously"

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  ～と同時どうじに has two main usages: ① Two actions happen at the same time, ② Two aspects are true simultaneously

• 

  For usage ①, と同時どうじに can attach to casual form verbs, and nouns

• 

  For usage ①, と同時どうじに tends to be used with instantaneous/quick actions

• 

  For usage ②, と同時どうじに can attach to casual form verbs/い-adjectives, and to nouns/な-adjectives using である