Ajam (عجم) is an Arabic word meaning mute, which today refers to someone whose mother tongue is not Arabic. During the Arab conquest of Persia, the term became a racial pejorative. in many languages—including Persian, Turkish, Urdu, Azeri, Bengali, Hindi, the Kurdish languages, Pashto, Gujarati, Malay, Punjabi, and Swahili—Ajam and Ajami refer to Persia and Persians respectively.
Homophonous words, which may or may not be derived from the same root, include:
Modern use of "ajam" has the meaning of "non-Arab". Its development from meaning "mute" to meaning "non-Arabic-speaking" is somewhat analogous to that of the word barbarian (< Greek βαρβαρόφωνος barbarophonos).
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The verb ʿajama originally meant "to mumble, and speak indistinctly", which is the opposite of ʿaraba, “to speak clearly”. Accordingly, the noun ʿujma, of the same root, is the opposite of fuṣḥa, which means "chaste, correct, Arabic language". In general, during the Umayyad period ajam was a pejorative term used by Arabs who believed in their social and political superiority, in early history after Islam. However, the distinction between Arab and Ajam is discernible in pre-Islamic poetry.
According to the book "Documents on the Persian Gulf's name"[additional citation(s) needed], the word Ajam has had many different uses and meanings throughout the history. The word had a simple meaning at first, but over time, other meanings and concepts are added to it, especially when the word was borrowed into other languages. Ajam has never meant dumb in Arabic; using it in a derogatory sense is a modern concept. Ajam was first used for Persian speakers in the poems of pre-Islamic Arab poets; after the advent of Islam it also referred to Turks, Zoroastrians, and others. Today, in Arabic literature, Ajam is used to refer to all non-Arabs. An alternate etymology derives the term from the mythological Persian Shah Jamshid. Nadr ibn al-Harith wrote a book about the stories of the Moluk of Ajam and presented it to the new Muslims as more important than the stories of Muhammad. Al-A'sha, another famous pre-Islamic poet from Najd, had written poems describing the Ajami kings one of the Al-A'sha poem is:" أَوْ عَاتِقًا مِنْ أَذْرُعَاتٍ مُعَتَّقًا مِمَّا تَعَتَّقَهُ مُلُوكُ الأَعْجَمِ For the first time in the Umayyad period, the derogatory use of the word Ajam applied to the Persians. but during Abbasid and after The word Ajam was used for the Persians not only for humiliating but also a source of pride, as some Arabs even in The pre-Islamic period proudly narrated the glorious stories of the Molouk(kings) of Ajam and the Molk of Jam (Persia).the Arab poets Yaqut al-Hamawi and Al-Mutawakkil wrote: "I am the son of the honors Offspring of Jam(jamshid) holder of the glory legacy of Persian kings.انا ابن المکارم من النسل جم و حائز ارث ملوک العجم  during the period Iranian Intermezzo native Persian Muslim dynasties the word ajam and persian both were used to refer to Iranian.
Many Arabic sources refer to Persian language as Ajami language or Ajmo. Persian is the official language in Iran as "Parsi" and "Farsi", in Afghanistan as Parsi and Dari, and Tajiki in Tajikistan, Persian in Bahrain is called "Ajami" and in Kuwait "Ayami" . In classical Arabic, especially in the first centuries of the Islamic period, the Persian language was called "the language of the Ajam" لسان العجم, and the Iranian people were called the "Ajami" and the persian gulf was called Ajam Gulf, in many books and deed, Tafsir al-Zahak The oldest commentary on Quran wrote on page 524 " In Surah An-Nahl, verse 103,the word Ajami refers to Salman Farsi and says Ajami is the Persians. .also Arabic word for dictionary is mo'jam (moajam) that means definition of the non Arabs(ajam) word.
During the Umayyad period, the term developed a derogatory meaning as the word was used to refer to non-Arab speakers (primarily Persians) as illiterate and uneducated. Arab conquerors in that period tried to impose Arabic as the primary language of the subject peoples throughout their empire. Angry with the prevalence of the Persian language in the Divan and Persian society, Persian resistance to this mentality was popularised in the final verse of Ferdowsi's Shahnameh; this verse is widely regarded by Iranians as the primary reason that they speak Persian and not Arabic to this day. Under the Umayyad dynasty, official association with the Arab dominion was only given to those with the ethnic identity of the Arab and required formal association with an Arab tribe and the adoption of the client status (mawālī, another derogatory term translated to mean "slave" or "lesser" in this context). The pejorative use to denote Persians as "Ajam" is so ingrained in the Arab world that it is colloquially used to refer to Persians as "Ajam" neglecting the original definition and etymology of the word.
According to Clifford Edmund Bosworth, "by the 3rd/9th century, the non-Arabs, and above all the Persians, were asserting their social and cultural equality (taswīa) with the Arabs, if not their superiority (tafżīl) over them (a process seen in the literary movement of the Šoʿūbīya). In any case, there was always in some minds a current of admiration for the ʿAǰam as heirs of an ancient, cultured tradition of life. After these controversies had died down, and the Persians had achieved a position of power in the Islamic world comparable to their numbers and capabilities, "ʿAjam" became a simple ethnic and geographical designation.". Thus by the ninth century, the term was being used by Persians themselves as an ethnic term, and examples can be given by Asadi Tusi in his poem comparing the superiority of Persians and Arabs. Accordingly: "territorial notions of “Iran,” are reflected in such terms as irānšahr, irānzamin, or Faris, the Arabicized form of Pārs/Fārs (Persia). The ethnic notion of “Iranian” is denoted by the Persian words Pārsi or Irāni, and the Arabic term Ahl Faris (inhabitants of Persia) or ʿAjam, referring to non-Arabs, but primarily to Persians as in molk-e ʿAjam (Persian kingdom) or moluk-e ʿAjam (Persian kings).".
According to The Political Language of Islam, during the Islamic Golden Age, 'Ajam' was used colloquially as a reference to denote those whom Arabs in the Arabian Peninsula viewed as "alien" or outsiders. The early application of the term included all of the non-Arab peoples with whom the Arabs had contact including Persians, Byzantine Greeks, Ethiopians, Armenians, Assyrians, Mandaeans, Arameans, Jews, Georgians, Sabians, Samaritans, Egyptians, and Berbers.
During the early age of the Caliphates, Ajam was often synonymous with "foreigner" or "stranger". In the Western Asia, it was generally applied to the Persians, while in al-Andalus it referred to speakers of Romance languages - becoming "Aljamiado" in Spanish in reference to Arabic-script writing of those languages - and in West Africa refers to the Ajami script or the writing of local languages such as Hausa and Fulani in the Arabic alphabet. In Zanzibar ajami and ajamo means Persian which came from the Persian Gulf and the cities of Shiraz and Siraf. In Turkish, there are many documents and letters that used Ajam to refer to Persian.  pages 22-44
In the Persian Gulf region today, people still refer to Persians as Ajami, referring to Persian carpets as sajjad al Ajami (Ajami carpet), Persian cat as Ajami cats, and Persian Kings as Ajami kings.