adjective
simultaneous, at the same time
B1
Gleichzeitig means simultaneous or 'at the same time.' Used as adjective or adverb: as adjective it takes normal German endings; as adverb it remains uninflected. It's not gradable (no comparative). Antonym: nacheinander. Not a participle; no special preposition required. Common in descriptions of overlapping actions or events.
Examples
Die Konferenz fand gleichzeitig in drei Städten statt.
The conference took place simultaneously in three cities.
Er versucht, zu arbeiten und gleichzeitig seinem Sohn zuzuhören.
He tries to work and at the same time listen to his son.
Die beiden Prüfungen begannen gleichzeitig, sodass viele Studenten unter Druck gerieten.
The two exams started at the same time, so many students came under pressure.
Details
Mnemonics
Two clocks with their hands aligned showing the exact same time; both events happen together.
Think 'gleich' = 'same' + 'zeitig' ~ 'timing' → same timing.
Notes
'Gleichzeitig' is used to describe events occurring at the same moment. As an adjective/adverb it often collocates with verbs of happening or action. It is not commonly used in comparative forms.