On the other hand, immediately after the Basmala and sometimes before the title, 29 twenty-nine Qurʾānic Suras have so-called “Mysterious Letters,” i. e. a single letter or a one- or two-word combination of up to five letters each. These letters cannot be read as proper Arabic and have been interpreted very differently by scholars old and new. For the Mysterious Letters, see Loth 1881, 603‒610; Meyer 1912, 82 n.1; Nöldeke/Schwally 1919/1961, 68‒78; Bauer 1921; Goossens 1923; Jeffery 1924 (who mostly quotes Goossens); Blachère 1959/1991, 29; 46‒47; 138; 144‒149; Seale 1959/1975; Jones 1962; Speight 1969, 206; 208; Watt 1970/1977, 61‒65; 90; 138; 140; 144; Bellamy 1973; Neuwirth 1981/2007, 105; Nagel 1983, 145‒147; Neuwirth 1991, 32; Schmucker 1995; Kandil 1996a, 37; Massey 1996; Shahîd 2000; Welch 2000, 79 (and 111‒112 n. 8); Böwering 2001, 326‒327; Madigan 2001a, 40‒42; Massey 2003; Robinson 2003, 260‒270; Ambros/Procházka 2004, 367‒368; Wild 2006a, 20; Hoffmann 2007, 101‒106; Neuwirth 2007, 21*; Sinai 2009, 36; Dayeh 2010, 462‒464; Neuwirth 2010, 147; 174; 246‒249; 323; 361‒362; 436; 448‒449; 454 (“sakrale Intonation”); 464 (“Intonation”); Stewart 2011, 339‒347; Bannister 2014, 174 (and 204 n. 7); Boisliveau 2014a, 97‒101; Sinai 2016, 137; Sinai 2017c, 26‒28; 109.
Mysterious Letters do not correlate with the seven prologue types. However, Suras with the Mysterious Letters ʾlmr, ḥm ʿsq, ṭh, q, khyʿṣ, n, ṣ, and ys³⁹ do correlate with and go beyond al-raḥmān Suras, while Suras with Mysterious Letters ʾlr, ʾlm, ʾlmṣ, ḥm, ṭs and ṭsm correlate with and go beyond rabb al-ʿālamīn Suras (including mixed Suras 2, 26, 41, and 43). Thus we have: (a) an enlarged al-raḥmān group of 12 Suras (Q 13; 17; 19; 20; 21; 25; 36; 38; 50; 55; 67; 78); (b) an enlarged rabb al-ʿālamīn group of 29 Suras (Q 2, with al-raḥmān and rabb al-ʿālamīn each once; 3; 6; 7; 10; 11; 12; 14; 15; 26, mostly rabb al-ʿālamīn, once al-raḥmān; 27; 28; 29; 30; 31; 32; 37; 39; 40; 41, with al-raḥmān and rabb al-ʿālamīn each once; 42; 43, with mostly al-raḥmān, once rabb al-ʿālamīn; 44; 45; 46; 56; 69; 81; 83); and (c) just 1 Sura in the mixed al-raḥmān-and-rabb al-ʿālamīn category (Q 59).