The letter kaf is one of the six letters which can receive a dagesh kal. The other five are bet, gimel, daleth, pe, and tav. There are two orthographic variants of this letter which alter the pronunciation:
When the kaph has a "dot" in its center, known as a dagesh, it represents a voiceless velar plosive. There are various rules in Hebrew grammar that stipulate when and why a dagesh is used.
Kaf without the dagesh (khaf)
When this letter appears as without the dagesh in its center it represents, like the ch in German "Bach". In modern Israeli Hebrew the letter heth is often pronounced as a, but many communities have differentiated between these letters as in other Semitic languages.
If the letter is at the end of a word the symbol is drawn differently. However, it does not change the pronunciation or transliteration in any way. The name for the letter is final kaf. Four additional Hebrew letters take final forms: tsadi, mem, nun, and pei. Kaf/khaf is the only Hebrew letter that can take a vowel in its word-final form which is pronounced after the consonant, that vowel being the qamatz.
Significance of kaph in Hebrew
In gematria, kaph represents the number 20. Its final form represents 500, but this is rarely used, tav and qoph being used instead. As a prefix, kaph is a preposition:
It can mean "like" or "as", as in literary Arabic.
In colloquial Hebrew, kaph and shin together have the meaning of "when". This is a contraction of, ka'asher.
Arabic kāf
The letter is named kāf, and it is written in several ways depending on its position in the word. There are three variants of the letter:
the basic form is used for the Arabic language and many other languages:
the cross-barred form, notably 'al-kāf al-mashkūlah/al-mashqūqah, is used predominantly as an alternative form of the version above in all forms of Arabic and in the languages that use the Perso-Arabic script.
the long s-shaped variant form, al-kāf al-mabsūṭah, which is used in Arabic texts and for writing the Qur'an. It has a particular use in the Sindhi language of Pakistan, where it represents the unaspirated /k/, in contrast to the aspirated /kʰ/, which is written using the "normal" kāf ک.
In Literary Arabic, kāf is used as a prefix meaning "like", "as", or "as though". For example, كَطَائِر, meaning "like a bird" or "as though a bird". The prefix كَـ ka is one of the Arabic words for "like" or "as". The prefix sometimes has been added to other words to create fixed constructions. For instance, it is prefixed to ذٰلِك "this, that" to form the fixed word كَذٰلِك "like so, likewise." kāf is used as a possessive suffix for second-person singular nouns ; for instance, كِتَاب kitāb becomes كِتَابُكَ kitābuka كِتَابُكِ kitābuki. At the ends of sentences and often in conversation the final vowel is suppressed, and thus كِتَابُك kitābuk. In several varieties of vernacular Arabic, however, the kāf with no harakat is the standard second-person possessive, with the literary Arabic harakah shifted to the letter before the kāf: thus masculine "your book" in these varieties is كِتَابَك kitābak and feminine "your book" كِتَابِك kitābik.