Question: The alphabet of which the letter Sad is a part includes how many letters?

Context paragraphs:
Khowar alphabet: The Khowar alphabet is the right-to-left alphabet used for the Khowar language.  It is a modification of the Urdu alphabet, which is itself a derivative of the Persian alphabet and Arabic alphabet.  According to the Khowar Academy with 60 letters, the Khowar alphabet is typically written in the calligraphic Nasta'liq script, whereas Arabic is more commonly in the Naskh style.  Usually, bare transliterations of Khowar into Roman letters omit many phonemic elements that have no equivalent in English or other languages commonly written in the Latin script.  The Khowar Academy of Pakistan has developed a number of systems with specific notations to signify non-English sounds, but these can only be properly read by someone already familiar with Khowar, Persian, or Arabic for letters such as:ژ خ غ ط ص or ق and Hindi for letters such as ڑ .

SaypU: SaypU or SaypYu ( ) is an acronym for "Spell As You Pronounce Universally" (in SaypU "Spel az Yu Prɘnawns Yunivɘɘrsɘlli") is an approximative phonetic alphabet of 24 alphabet letters to spell languages, including English.  The spelling system was adopted by Jaber George Jabbour to write English more phonetically.  The 24-letter alphabet includes 23 Roman alphabet letters (after excluding "c", "q" and "x") and the addition of a 24th letter, the IPA letter "ɘ" (close-mid central unrounded vowel) to play the role of schwa.  The letter represents the initial sound of "ago" or "about".

Dž: ǅ (titlecase form; all-capitals form Ǆ, lowercase ǆ) is the seventh letter of the Gaj's Latin alphabet for Serbo-Croatian (Bosnian, Croatian, Montenegrin and Serbian), after D and before Đ.  It is pronounced d͡ʒ] .  Dž is a digraph that corresponds to the letter Dzhe (Џ/џ) of the Serbian Cyrillic alphabet.  It is also the tenth letter of the Slovak alphabet.  Although several other languages (see below) also use the letter combination "DŽ", they treat it as a pair of the letters "D" and "Ž", not as a single distinct letter.

Guarani Braille: Guarani Braille is the braille alphabet of the Paraguayan Guarani language.  Letter assignments are those of Spanish Braille (except for the accented vowels): that is, the basic braille alphabet plus for "ñ".  An additional letter, , is used for glottal stop, written as an apostrophe in the Guarani print alphabet.  Print digraphs such as "ch" and "rr" are digraphs in braille as well.  In addition, the tilde in print is written as the letter in braille, and comes before the letter it appears on in print.  Thus the Guarani letters outside the basic Latin alphabet are:

Filipino alphabet: The Modern Filipino alphabet (Filipino: "Makabagong alpabetong Filipino" ), otherwise known as the Filipino alphabet (Filipino: "alpabetong Filipino" ), is the alphabet of the Filipino language, the official national language and one of the two official languages of the Philippines.  The Modern Filipino alphabet is made up of 28 letters, which includes the entire 26-letter set of the ISO basic Latin alphabet, the Spanish "Ñ" and the "Ng" digraph of Tagalog.  It replaced the Pilipino alphabet of the Fourth Republic.  Today, the Modern Filipino alphabet may also be used as the alphabet for all autochthonous languages of the Philippines and in writing Chavacano, a Spanish-derived creole.

Arabic alphabet: The Arabic alphabet (Arabic: الأَبْجَدِيَّة العَرَبِيَّة‎ ‎ "al-abjadīyah al-ʻarabīyah ", or الحُرُوف العَرَبِيَّة "al-ḥurūf al-ʻarabīyah ") or Arabic abjad is the Arabic script as it is codified for writing the Arabic language.  It is written from right to left in a cursive style and includes 28 letters.

Archaic Greek alphabets: Many local variants of the Greek alphabet were employed in ancient Greece during the archaic and early classical periods, until they were replaced by the classical 24-letter alphabet that is the standard today, around 400 BC.  All forms of the Greek alphabet were originally based on the shared inventory of the 22 symbols of the Phoenician alphabet, with the exception of the letter Samekh, whose Greek counterpart Xi (Ξ) was used only in a sub-group of Greek alphabets, and with the common addition of Upsilon (Υ) for the vowel /u, ū/.  The local, so-called "epichoric", alphabets differed in many ways: in the use of the consonant symbols Χ, Φ and Ψ; in the use of the innovative long vowel letters (Ω and Η), in the absence or presence of Η in its original consonant function (/h/); in the use or non-use of certain archaic letters (Ϝ = /w/, Ϙ = /k/, Ϻ = /s/); and in many details of the individual shapes of each letter.  The system now familiar as the standard 24-letter Greek alphabet was originally the regional variant of the Ionian cities in Asia Minor.  It was officially adopted in Athens in 403 BC and in most of the rest of the Greek world by the middle of the 4th century BC.

Urdu alphabet: The Urdu alphabet is the right-to-left alphabet used for the Urdu language.  It is a modification of the Persian alphabet known as Perso-Arabic, which is itself a derivative of the Arabic alphabet.  The Urdu alphabet has up to 58 letters.  With 39 basic letters and no distinct letter cases, the Urdu alphabet is typically written in the calligraphic Nastaʿlīq script, whereas Arabic is more commonly in the Naskh style.

Abecedarius: An abecedarius is an acrostic in which the first letter of every word, strophe or verse follows the order of the alphabet.  Abecedarius is also a generic term for an alphabet book, which dates back to Biblical writings such as the Psalms, which used successive letters of the Hebrew alphabet as the first letter of each stanza.  Another example is Old Polish poem "Skarga umierającego" ("A Dying Man Complaint").  Such poems are important historical sources for development of orthography.  They can be proofs that some letters were used long ago and later were totally forgotten.  Bishop Constantine of Preslav's abecedarius (shown on the right) from 9th century documents the early Slavic alphabet.  Nowadays abecedariuses are written chiefly for children.

Sad (surah): Sūrat Ṣād (Arabic: سورة ص‎ ‎ , "The Letter Sad") is the 38th sura of the Qur'an with 88 ayat and 1 sajdah (39:24).  Sad (ص) is the name of the eighteenth letter in the Arabic alphabet.

Supporting paragraphs: Sad (surah) Arabic alphabet
Answer: 28