Things that are simultaneous happen at exactly the same time — not one after the other, and not merely in the same afternoon. If the lights go on and the music starts in the same instant, those two events are simultaneous.

Things that are simultaneous simultaneous 的事情 happen at exactly the same time是在完全相同的時間發生的 not one after the other不是先後發生 and not merely in the same afternoon也不只是同一個下午發生而已 If the lights go on and the music starts in the same instant如果燈亮起和音樂響起是在同一瞬間 those two events are simultaneous這兩件事就是 simultaneous 的

A simultaneous translation is a voice in another language while the first speaker is still talking, not after they finish. In school maths, simultaneous equations are a set that are all true together, so you solve them as a group.

A simultaneous translation simultaneous translation（同步口譯） is a voice in another language while the first speaker is still talking是講者還在說話時，同時傳來的另一種語言的聲音 not after they finish而不是等他講完之後 In school maths在學校數學裡 simultaneous equations simultaneous equations（聯立方程式） are a set that are all true together是一組必須同時成立的方程式 so you solve them as a group所以你要把它們當成一組一起解

The everyday phrase is “at the same time”; simultaneous is the more careful school-and-news word. Though actually, people do stretch it to mean “in the same period.” Strict speakers keep it for the same moment. The adverb is a different shape: simultaneously. “The two phones rang simultaneously.”

The everyday phrase is "at the same time"日常說法是「at the same time」 simultaneous is the more careful school-and-news word而 simultaneous 是比較講究的學術和新聞用字 Though actually不過其實 people do stretch it to mean "in the same period."有人會把它用得比較鬆，指「在同一段期間」 Strict speakers keep it for the same moment嚴謹的人則堅持只用在同一瞬間 The adverb is a different shape副詞的形式不一樣： simultaneously simultaneously "The two phones rang simultaneously."「The two phones rang simultaneously」（兩支電話同時響了）