reflex
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reflex
An involuntary, very quick and automatic reaction of the body to an external stimulus, which is not consciously controlled.
Der Arzt prüfte mit einem Hämmerchen den Kniesehnenreflex des Patienten.
The doctor tested the patient's patellar reflex with a small hammer.
The meaning is easy to recognize from context. If people are talking about medicine, biology, or the body, the physical reaction is meant. If it is about a spontaneous reaction to a situation or news, the figurative meaning is meant.
Das Schließen des Augenlids bei Berührung ist ein wichtiger Reflex.
Closing the eyelid when touched is an important reflex.
In the medical meaning, 'Reflex' (reflex) is often combined with verbs like 'testen' (to test), 'prüfen' (to check/test), or 'auslösen' (to trigger). It is also often part of compound words that describe the reflex more precisely (e.g., Schutzreflex, protective reflex).
Ein lautes Geräusch kann einen Schreckreflex auslösen.
A loud noise can trigger a startle reflex.
A very common expression is 'aus Reflex handeln' (to act on reflex) or 'etwas aus Reflex tun' (to do something on reflex). This means that someone reacts automatically and without thinking.
Als der Ball auf ihn zuflog, hob er aus Reflex die Hände.
When the ball flew toward him, he raised his hands on reflex.
In the figurative meaning, the structure 'mein/sein/ihr erster Reflex war, ... zu ...' (my/his/her first reflex was to ...) is often used to describe a spontaneous first reaction or first thought.
Mein erster Reflex war, sofort „Nein“ zu sagen.
My first reflex was to say 'No' immediately.
reaction
'die Reaktion' and 'der Reflex' both describe something happening as a response to a stimulus or a situation. 'die Reaktion' is more general and can be conscious or unconscious. It can be physical, but it can also consist of words or behavior. 'der Reflex' is a very quick, automatic reaction that you do not consciously control. In a figurative sense, too, 'Reflex' means something you do immediately and without much thought. Learners may confuse the words because every reflex is a reaction. But not every reaction is a reflex.
Beim Training zog Frau Meier die Hand aus Reflex sofort zurück.
During training, Ms. Meier immediately pulled her hand back by reflex.
Meine Schwester wartet am Telefon auf seine Reaktion.
My sister is waiting on the phone for his reaction.