As explained in Chapter 2, tone languages use pitch contrasts to keep words apart, in the same way that languages use vowel and consonant contrasts for this purpose. Mandarin, for instance, has four lexically contrastive pitch patterns. In (1a,b,c,d) these pitch patterns are illustrated with four words that minimally differ for tone, a ‘minimal quadruplet’. In (1e) a fifth word is given, which has the same tone as (1d) but has a different consonant, and so forms a minimal pair with (1d). Other languages that use tone contrasts for lexical purposes can be found in south-east Asia, Africa and the Americas.