Latin through the influence of written language and the liturgical language of the Church. The loanwords were taken from both Classical Latin and Renaissance Latin, the form of Latin in use at that time. According to the theories of Ramón Menéndez Pidal, local sociolects of Vulgar Latin evolved into Spanish, in the north of Iberia, in an area centered in the city of Burgos, and this dialect was later brought to the city of Toledo, where the written standard of Spanish was first developed, in the 13th century. In this formative stage, Spanish developed a strongly differing variant from its close cousin, Leonese, and, according to some authors, was distinguished by a heavy Basque influence (see Iberian Romance languages). This distinctive dialect spread to southern Spain with the advance of the , and meanwhile gathered a sizable lexical influence from the Arabic of Al-Andalus, much of it indirectly, through the Romance Mozarabic dialects (some 4,000 Arabic-derived words, make up around 8% of the language today). The written standard for this new language was developed in the cities of Toledo, in the 13th to 16th centuries, and Madrid, from the 1570s. The development of the Spanish sound system from that of Vulgar Latin exhibits most of the changes that are typical of Western Romance languages, including lenition of intervocalic consonants (thus Latin > Spanish ). The diphthongization of Latin stressed short and —which occurred in open syllables in French and Italian, but not at all in Catalan or Portuguese—is found in both open and closed syllables in Spanish, as shown in the following table: Spanish is marked by palatalization of the Latin double consonants (geminates) and (thus Latin > Spanish , and Latin > Spanish ). The consonant written or in Latin and pronounced in Classical Latin had probably "fortified" to a bilabial fricative in Vulgar Latin. In early Spanish (but not in Catalan or Portuguese) it merged with the consonant written b (a bilabial with plosive and fricative allophones). In modern Spanish, there is no difference between the pronunciation of orthographic and . Typical of Spanish (as also of neighboring Gascon extending as far north as the Gironde estuary, and found in a small area of Calabria), attributed by some scholars to a Basque substratum was the mutation of Latin initial into whenever it was followed by a vowel that did not diphthongize. The , still preserved in spelling, is