General weakness:
* Faible: This is the most common and general word for "weak". It can describe physical, mental, or emotional weakness.
* Fragile: This implies a delicate and easily breakable weakness.
Specific weaknesses:
* Pauvre: This means "poor" and can be used to describe a weak quality, like "poor eyesight" (une pauvre vue).
* Déficient: This refers to a specific deficiency or lack of something, like "deficient in vitamin D" (déficient en vitamine D).
* Manquant: This means "missing" and can be used to describe a lack of something important, like "lacking in courage" (manquant de courage).
Informal or colloquial:
* Mou: This is a more informal and slang term for "weak", often used to describe someone who is easily intimidated or influenced.
* Flétri: This is a more literary term for "weak" and often carries a negative connotation.
The best way to choose the right word is to consider the context and the specific meaning you want to convey.