Numerical digit
From India, the thriving trade between Islamic sultans and Africa carried the concept to Cairo. Arabic mathematicians extended the system to include decimal fractions, and Muḥammad ibn Mūsā al-Ḵwārizmī wrote an important work about it in the 9th  century. The modern Arabic numerals were introduced to Europe with the translation of this work in the 12th century in Spain and Leonardo of Pisa's "Liber Abaci" of 1201. In Europe, the complete Indian system with the zero was derived from the Arabs in the 12th century.
Islamic world contributions to Medieval Europe
A number of technologies in the Islamic world were adopted in European medieval technology. These included various crops; various astronomical instruments, including the Greek astrolabe which Arab astronomers developed and refined into such instruments as the "Quadrans Vetus", a universal horary quadrant which could be used for any latitude, and the "Saphaea", a universal astrolabe invented by Abū Ishāq Ibrāhīm al-Zarqālī; the astronomical sextant; various surgical instruments, including refinements on older forms and completely new inventions; and advanced gearing in waterclocks and automata. Distillation was known to the Greeks and Romans, but was rediscovered in medieval Europe through the Arabs. The word alcohol (to describe the liquid produced by distillation) comes from Arabic "al-kuhl". The word alembic (via the Greek Ambix) comes from Arabic "al-anbiq". Islamic examples of complex water clocks and automata are believed to have strongly influenced the European craftsmen who produced the first mechanical clocks in the 13th century.