simultaneously

This adverb describes events occurring at the exact same moment in time. It is frequently used in technical, scientific, or formal contexts to emphasize precise synchronization, such as multiple computer processes running at once or a musician playing two notes at the same time.

While "at the same time" is a common synonym, "simultaneously" carries a more formal register and often implies a tighter, more instantaneous alignment of events. It is rarely used in very casual conversation, where the phrasal equivalent is preferred.