 This list does not include commonplace extensions of the IPA, such as doubling a symbol for a greater degree of a feature ( extra-long , extra stress, strongly aspirated , and extra-rhotic ), nor superscripting for a lesser degree of a feature ( slightly prenasalized , slightly affricated , and epenthetic schwa).The asterisk, as in for the fortis stop of Korean, is the convention the IPA uses when it has no symbol for a phone or feature.For symbols and values which were discarded by 1932, see History of the International Phonetic Alphabet.