我不确定。

You can use this phrase as a standalone answer or at the start of a sentence. If someone asks if the train leaves at 5 PM, just say 我不确定. If you want to be more specific, follow it with the thing you're unsure about. For example: 我不确定他会来 (I'm not sure he will come). It’s very flexible. You can also add 还 (hái) to say 我还不敢确定 if you want to sound even more cautious, like you're still waiting for more info.

Use it whenever you want to avoid being wrong. It’s perfect for a restaurant when a friend asks if the food is spicy. It’s great at work when a boss asks for a deadline you haven't checked. It's also useful in texting when someone asks for your weekend plans. It makes you sound thoughtful rather than impulsive. It’s the ultimate 'safety first' phrase for your social life.

Don't use it if you actually know the answer but are just being shy. In Chinese culture, being overly vague can sometimes be frustrating. Avoid it if a clear 'yes' or 'no' is required for safety or urgent matters. If your doctor asks if you're allergic to peanuts, 'I'm not sure' is a scary answer! Also, don't use it if you simply don't care; in that case, other phrases might fit better.

Chinese communication often values 'saving face' and avoiding direct conflict. Saying 我不确定 is a soft way to decline an invitation or avoid making a promise you can't keep. It provides a 'buffer zone.' Historically, directness wasn't always prized in social hierarchy. By being 'unsure,' you leave room for others to provide their input without being corrected by you. It’s a subtle tool for social harmony.

You might hear 我不敢确定 (wǒ bù gǎn quèdìng), which means 'I don't dare to be sure.' This adds a layer of humility. In casual settings, people might just say 不确定 (bù quèdìng) to save time. If you are really unsure, you can say 我真不确定 (wǒ zhēn bù quèdìng). Each variation just tweaks the 'volume' of your uncertainty. It's like turning a dial on a radio.