noun
fever
A1
Fieber (das) means 'fever' (medical elevated body temperature). Plural is Fieber (unchanged). Declensions: genitive singular des Fiebers, plural dative den Fiebern. Neuter gender. Typically uncountable when speaking of the condition, but can be pluralized to refer to multiple fevers or episodes.
Examples
Wenn man Fieber hat, sollte man im Bett bleiben.
If you have a fever, you should stay in bed.
Das Kind hat hohes Fieber.
The child has a high fever.
Weil das Kind hohes Fieber hatte, rief die Lehrerin die Eltern an und bat sie, das Kind abzuholen.
Because the child had a high fever, the teacher called the parents and asked them to pick up the child.
Details
Mnemonics
picture a thermometer reading high over the word 'Fieber'
sounds like 'fibber' — when you have a fever you might feel like a 'fibber' telling stories (silly association)
das = neutral; imagine a thermometer (object) to anchor 'das Fieber'
Notes
Usually treated as an uncountable medical symptom, but 'Fieber' can be plural when talking about individual fever episodes ('hohe Fieber' is rare).