当某人 lights up，这意味着他/她看起来很高兴或为什么事情而感到欣喜。
- Mum will light up when she realises we've planned a surprise party for her.
- My grandma would light up when she talked about the olden days.
值得注意的是，另一个字面相似的短语 lighten up 意思和 light up 不一样，这是劝某人应该放松一些，不要太紧张或太在意某件事情。
- Hurry! We're going to miss the train!
- Lighten up – there'll be another one five minutes later.
