Inventory differences

The stock of phonemes a speaker uses is known as his/her phoneme inventory. RP speaker has around 21 vowel and 24 consonant phonemes, but the precise number may vary: not all RP speakers use all the centring diphthongs, for example. An important difference in phoneme inventory distinguishes northern and southern varieties of English English: because of a historical vowel split which happened in the south, southern varieties have an additional phoneme  which northern varieties lack. This means that southern speakers have a  phonemic contrast for pairs such as cud/could, putt/put, which are homophonous for northerners ([ and  respectively). Scottish English varieties have an additional consonant phoneme /x/ which English English varieties lack, meaning that loch  and lock  are generally distinguished north of the border, but not south of it ( in both cases).