weakness
The German word "Schwäche" is the direct translation of the English word "weakness". It is used to describe a lack of strength, whether physical, mental, or emotional. It can also refer to a flaw or vulnerability in a person's character or abilities. In a sentence, you might say "Seine Schwäche ist Mathematik", which translates to "His weakness is mathematics". Please note that nouns in German are always capitalized.
His biggest weakness are his feet.
This phrase could be used to talk about someone who maybe isn't very good at sports involving their feet, like soccer, or someone who has physical problems with their feet.
Your knowledge of physics is a weakness.
This phrase could be used when someone does not have adequate knowledge in a specific area, such as Physics, making it a weak point for them.
He has a weakness for chocolate ice cream.
This phrase can be used when someone is very fond of something, in this case, chocolate ice cream, to the extent that it could be seen as a 'weakness' for them.