die Übelkeit
nausea
The unpleasant feeling in the stomach that often comes before vomiting; also referred to as nausea.
Die kurvige Fahrt verursachte bei ihr starke Übelkeit.
The winding drive caused her severe nausea.

nausea
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nausea
The unpleasant feeling in the stomach that often comes before vomiting; also referred to as nausea.
Die kurvige Fahrt verursachte bei ihr starke Übelkeit.
The winding drive caused her severe nausea.

'Übelkeit' (nausea) is the noun related to the adjective 'übel' (sick/nauseous). If a person 'übel ist' (feels sick), then they have 'Übelkeit' (nausea). The suffix '-keit' forms nouns from adjectives that describe a state or quality.
Mir ist übel, ich glaube, ich habe Übelkeit.
I feel sick; I think I have nausea.
To express that you have this feeling, you often use the phrases 'Übelkeit haben' (to have nausea), 'Übelkeit verspüren' (to feel nausea), or 'an Übelkeit leiden' (to suffer from nausea). The latter is used more for longer-lasting or serious complaints.
Seit heute Morgen verspüre ich eine leichte Übelkeit.
Since this morning, I have been feeling slight nausea.
'Übelkeit' often occurs together with other symptoms. Common combinations are 'Übelkeit und Erbrechen' (nausea and vomiting) or 'Übelkeit und Schwindel' (nausea and dizziness). You can also say 'Übelkeit bekämpfen' (to combat nausea) or 'etwas gegen Übelkeit tun' (to do something for nausea).
Reisetabletten helfen gegen Übelkeit und Erbrechen.
Travel sickness tablets help with nausea and vomiting.
unease / discomfort
'die Übelkeit' and 'das Unbehagen' both describe an unpleasant feeling. However, 'Übelkeit' is much more specific: it refers to a bad feeling in the stomach, often shortly before vomiting. 'Unbehagen' is more general. It can be slight physical discomfort, but also an inner, uncertain, or tense feeling in a situation. Learners may confuse the words because both have to do with 'not feeling well'. If the stomach is affected, you say 'Übelkeit'. If the feeling is less clear or more psychological, 'Unbehagen' fits better.

Nach der Busfahrt war die Übelkeit so stark, dass ich mich hinsetzen musste.
After the bus ride, the nausea was so strong that I had to sit down.
Mehmet spürt vor dem wichtigen Termin ein leichtes Unbehagen.
Mehmet feels a slight unease before the important appointment.