* Focusing on environmental sustainability: "The company is committed to sustainable practices, reducing its carbon footprint and using recycled materials."
* Focusing on economic sustainability: "The project aims for sustainable economic growth that benefits both the community and the environment."
* Focusing on social sustainability: "Sustainable development requires addressing social equity alongside environmental and economic concerns."
* Describing a product or system: "This sustainable fishing method ensures the long-term health of the fish population."
* Describing a lifestyle: "They live a sustainable lifestyle, minimizing waste and consuming locally sourced food."
* In a more general sense: "Finding sustainable solutions to climate change is crucial for future generations."
The key is to specify *what* is sustainable. Simply saying "That's sustainable" is grammatically correct but lacks context. You need to clarify what aspect of sustainability you're referring to.