Shaddah

Shaddah (Arabic: شَدّة shaddah [ˈʃæd.dæ], "[sign of] emphasis", also called by the verbal noun from the same root, tashdid تشديد tashdīd "emphasis") is one of the diacritics used with the Arabic alphabet, indicating a geminated consonant.

It is functionally equivalent to writing a consonant twice in the orthographies of languages like Latin, Italian, Swedish, and Ancient Greek, and is thus rendered in Latin script in most schemes of Arabic transliteration, e.g. رُمّان = rummān 'pomegranates'.

It was devised for poetry by al-Khalil ibn Ahmad in the eighth century, replacing an earlier dot.

In Unicode representation, the shaddah can appear either before or after the vowel diacritic, and most modern fonts can handle both options.

Stress falls on the first long syllable from the end of the word, hence أَقَلّ aqáll (or, with iʻrāb, aqállu) as opposed to أَكْبَر ákbar, مَحَبّة maḥábbah "love, agape" as opposed to مَعْرِفة maʻrifah '(experiential) knowledge'.