German names most symptoms with haben and a bare noun: ich habe Fieber, ich habe Husten, ich habe Halsschmerzen. The words for aches are plural-only compounds ending in -schmerzen, so they always take a plural verb and never an article.
Examples
- Ich habe Fieber und Halsschmerzen.
- I have a fever and a sore throat.
- Mein Sohn hat seit Montag Husten.
- My son has had a cough since Monday.
- Hast du Kopfschmerzen?
- Do you have a headache?
The mistake to avoid
Kopfschmerzen is always plural - never "ein Kopfschmerz".
Where this fits in
Body, health & feelings, German A2: Talk about your body, common illnesses, and how you feel. Visit a doctor or pharmacy and describe symptoms.