同時に vs. 一斉に: Their Difference is Just One Thing
What is the difference between “同時に(doujini) and 一斉に(isseini)”? Which is used for everybody doing something? After reading this, you would be answering this question. Let me introduce what their subtle differences are and how you correctly use them such as native speakers today!
同時に(doujini) / 一斉に(isseini)
At the same time or Simultaneously, At once / 同时, 一起 / 동시에, 일제히 / đồng thời, cùng một lúc
“同時に(doujini)” means “At the same time or Simultaneously” and “一斉に(isseini)” means ” At once” and which both have been used as the meaning of “happening or being done at exactly the same time”. The basic way to use it is “Aは同時に___する。(A ___ at the same time.)” and “Aは一斉に___する。(A ___ at once.)”, etc. For instance, “ゆかとたつやは同時に喋る。(Yuka and Tatsuya talk at the same time.)” and “１０人が一斉に喋る。(10 people talk at once.)”, etc. The tips for using them are that basically “同時に” and “一斉に” are the same meaning, however, “一斉に” sounds “MANY PEOPLE” do something simultaneously, it’s not two or three, like five, ten, twenty or more people. Whereas “同時に” sounds “TWO OR THREE PEOPLE” do something Simultaneously. For instance, a class has 30 children and say something simultaneously, that would be used “一斉に”, whereas a class has two children say something simultaneously, that would be used “同時に”. Everybody could use these as casual, polite and formal such as “ゆかとたつやは同時に喋ったね。(Yuka and Tatsuya talked at the same time.)” and “１０人が一斉に喋ったね。(10 people talked at once.)” as casual. And “ゆかとたつやは同時に喋りました。(Yuka and Tatsuya talked at the same time.)” and “１０人が一斉に喋りました。(10 people talked at once.)” as polite and formal.