* Describing physical strength: "After the surgery, he felt weak and needed assistance."
* Describing a lack of intensity: "The tea was weak and tasteless."
* Describing a flaw or vulnerability: "The enemy's defense was weak at the river crossing."
* Describing a character trait: "He had a weak will and often gave in to temptation."
* Describing a signal or connection: "The Wi-Fi signal was weak in the basement."
* Describing something unconvincing or ineffective: "Her argument was weak and unconvincing."
* In a comparative sense: "Compared to steel, wood is weak."
The best way to use "weak" depends entirely on the context and what you're trying to describe.