Can vs. Could

"Can you help me?" is direct. "Could you help me?" is softer. The difference is not grammar — it is social temperature. "Can" states ability or asks bluntly. "Could" adds a layer of distance that native speakers read as respect. Use "can" with friends and "could" with strangers, bosses, or anyone you want to impress.

"Could" also expresses past ability and hypothetical possibility. "I could swim when I was five" looks backward. "We could leave early" suggests a possibility that has not been decided yet. Context tells your listener which meaning you intend. If this sounds ambiguous, relax — native speakers rely on context too.