What it means
と同時に expresses that two events occur at the same time or that the second event begins immediately when the first event occurs. It follows a verb in the dictionary form or a noun that represents an event, action, or point in time. The construction is common in written and formal descriptions, especially when explaining processes, changes, or sequences of events.
Usage note
With a noun, noun + と同時に normally has a temporal meaning, such as “at the start of” or “when the event occurred.” It does not normally mean “at the same time as being” or indicate an additional role; that additive meaning requires a structure such as noun + であると同時に.
How to use it
開始と同時に式典の映像が会場のスクリーンに映し出されました。
At the start, footage of the ceremony was projected onto the screen at the venue.
研究チームは現地に到着すると同時に、調査を始めました。
The research team began the investigation as soon as it arrived at the site.
開始と同時に式典の映像が会場のスクリーンに映し出された。
At the start, footage of the ceremony was projected onto the screen at the venue.
研究チームは現地に到着すると同時に、調査を始めた。
The research team began the investigation as soon as it arrived at the site.