The I.T.A. symbol set includes joined letters (typographical ligatures) to replace the two-letter digraphs "wh", "sh", and "ch" of conventional writing, and also ligatures for most of the long vowels. There are two distinct ligatures for the voiced and unvoiced "th" sounds in English, and a special merged letter for "ng" resembling ŋ with a loop. There is a variant of the "r" to end syllables, which is silent in non-rhotic accents like Received Pronunciation but not in rhotic accents like General American and Scots English (this was the 44th symbol added to the I.T.A.).