noun
pain
A2
Schmerz (der) means 'pain' or 'ache' (physical or emotional). Use singular 'der Schmerz' and plural 'die Schmerzen' commonly for bodily pains. Genitive singular is 'des Schmerzes' (irregular -es). No special preposition required, though phrases often use 'Schmerzen haben' or 'Leiden an Schmerzen'.
Examples
Ich habe starke Schmerzen.
I have severe pain.
Die Krankenschwester verabreichte die Spritze gegen den Schmerz, damit der Patient besser schlafen konnte.
The nurse administered the injection against the pain so that the patient could sleep better.
Er hat Schmerzen im Rücken.
He has back pain.
Details
Mnemonics
imagine someone holding a sore spot and saying 'Schmerz!'
der (masculine) — picture a male figure pointing to the pain
Notes
Schmerz is often used in medical contexts and takes plural 'Schmerzen' when talking about pains/symptoms.