Free time

The character ‘空’ has two pronunciations, which are (kōng) and (kòng). In colloquial speech ‘有空’ is pronounced (yǒu kòng) and it means ‘have free time’. Here is an example, ‘我今天有空, 你呢?’ means ‘I have free time, how about you?’ when ‘空’is used in a word which has an indication towards ‘free’ the pronunciation is (kòng). However when ‘空’ is used in a word which has no relation to ‘free’ the pronunciation is (kōng). Here are two examples, ‘空闲’(kòng xián) means ‘leisure time’, and ‘天空’ (tiān kōng) means ‘sky’, notice the pronunciation difference between them.