Shaddah & Sukun
الشدّة والسكون
Doubling consonants and marking vowel absence
Shaddah (شدّة) is a diacritical mark shaped like a small "w" placed above a letter to indicate that the consonant is doubled — pronounced twice in succession. Sukun (سكون) is a small circle placed above a letter to indicate the absence of a vowel after that consonant. Together, they are essential to the Arabic diacritical system and directly affect pronunciation, rhythm, and meaning.
Typographic Impact
Shaddah is one of the tallest-stacking diacritics because it can combine with a vowel mark above it (e.g., shaddah + fathah, shaddah + dammah), creating multi-layered vertical stacks that push line spacing apart. Sukun is simpler but still requires careful placement to avoid colliding with dots or other marks. Both marks test a typeface's vertical metrics and spacing logic — poorly handled stacking can make fully vowelized text look crowded and hard to read.