Rasm

This concept is somewhat similar to scriptio continua in the Latin script, where all spaces and other punctuations is omitted.

[2] Signs indicating short vowels and the hamza are largely absent from Arabic orthography until the 2nd to 8th century.

One might assume that scribes would write these few diacritics in the most textually ambiguous places of the rasm, so as to make the Arabic text easier to read.

When speaking of the Qur'an, it stands for the basic text made of the 18 letters without the Arabic diacritics which mark vowels (taškīl) and disambiguate consonants (ʾiʿjām).

The rasm is the oldest part of the Arabic script; it has 18 elements, excluding the ligature of lām and alif.

[4] These signs, collectively known as ‘alāmātu-l-ihmāl, are still occasionally used in modern Arabic calligraphy, either for their original purpose (i.e. marking letters without ʾiʿjām), or often as purely decorative space-fillers.

The small ک‎ above the kāf in its final and isolated forms ⟨ك  ـك⟩ was originally ‘alāmātu-l-ihmāl, but became a permanent part of the letter.