Shaddah
Shaddah 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 such as for example Latin, Italian, Swedish, and Ancient Greek, and is rendered as such in Latin script in most schemes of Arabic transliteration, e.g. رُمَّان = .
Form
In shape, it is a small letter س s(h)īn, standing for shaddah. It was devised for poetry by Al-Khalil ibn Ahmad in the eighth century, replacing an earlier dot.| General Unicode | Name | Transliteration |
| 0651 ّ ّ |
Combination with other diacritics
When a is used on a consonant which also takes a [Arabic diacritics#Fatḥah|], the is written above the. If the consonant takes a [Arabic diacritics#Kasrah|], it is written between the consonant and the instead of its usual place below the consonant, however this last case is an exclusively Arabic language practice, not in other languages that use the Arabic script.For example, see the location of the diacritics on the letter ـهـ in the following words:
| Arabic | Transliteration | Meaning | Diacritic | Location of the diacritic |
| يَفْ | understands | Above the letter | ||
| فَ | explained | Above the | ||
| فَ | understood | Below the letter | ||
| فَ | explain! | Between the and the letter |
When writing Arabic by hand, it is customary first to write the and then the vowel diacritic.
In Unicode representation, the can appear either before or after the vowel diacritic, and most modern fonts can handle both options. However, in the canonical Unicode ordering the appears following the vowel diacritic, even though phonetically it should follow directly the consonantal letter.
Significance of marking consonant length
Consonant length in Arabic is contrastive: دَرَسَ ' means "he studied", while دَرَّسَ ' means "he taught"; بَكَىٰ صَبِيّ ' means "a youth cried" while بَكَّىٰ ٱلصَّبِيّ ' means "the youth was made to cry".A consonant may be long because of the form of the noun or verb; e.g., the causative form of the verb requires the second consonant of the root to be long, as in ' above, or by assimilation of consonants, for example the ' of the Arabic definite article al- assimilates to all dental consonants, e.g. ' instead of ', or through metathesis, the switching of sounds, for example أَقَلّ ' 'less, fewer', as compared to أَكْبَر ' 'greater'.
A syllable closed by a long consonant is made a long syllable. This affects both stress and prosody. Stress falls on the first long syllable from the end of the word, hence أَقَلّ ' as opposed to أَكْبَر ', مَحَبَّة "love, agape" as opposed to مَعْرِفَة ' ' knowledge'. In Arabic verse, when scanning the meter, a syllable closed by a long consonant is counted as long, just like any other syllable closed by a consonant or a syllable ending in a long vowel: أَلَا تَمْدَحَنَّ ' 'Will you not indeed praise...?' is scanned as : short, long, long, short, long, short.