The entries of every encyclopedia are tantamount to the broad outlines of its research project. Hence, the preparation of the entries is among the most sensitive and difficult stages of the definition of the project. The founders of The Encyclopaedia of the World of Islam, which encompasses a wide spectrum of the Islamic history, geography, culture and civilization as its main subject, appointed a board in 1990 to study the entries of the Encyclopaedia. The members of this board were: the Deputy for Scientific Affairs and Scientific Advisors, including Dr. Mahdi Mohaqeq, Dr. Mashyekh Faridani and Eng. Taromi as well as the late Dr. Taheri Araqi and Dr. Zaryab Khoei. In the beginning it was agreed to accept all the entries of the Encyclopedia of Islam (Brill) – except in exceptional cases – while improving the entries in the field of concepts of Islamic sciences and issues related to the Shiite history and culture and Islamic Iran by consulting other specialized sources. With the passage of time and given the significance of comprehensiveness of the entries and related issues, the procedure was changed and the methods of other encyclopedias were studied which included the Turk Endowment Encyclopedia, Encyclopedia of Islam in Urdu, Irannica, and the Persian Encyclopedia. Also the most important scientific texts in specialized fields were used for choosing the entries. From the early days of 1996, the task of selection the list of entries for different scientific departments were launched and after two years the final list of entries was prepared. However, given the fact that one-fifth of the Encyclopedia has been published, the scientific departments and the Entries Unit still are working on the list of entries to reevaluate them for any necessary changes.
Some of the principles for the selection of the entries in the Encyclopedia of the World of Islam are given below.
- Among different forms of a word, whether a name, concept or term, the most prevailing one is selected for the main entry and among the synonymous forms, the selection is based on the general criteria and similar entries and books written for the same purpose.
- The centers and cities of the Islamic world, whose names have been changed, are introduced with their latest names, such as Babel instead of Barforush.
- The cities and countries that had already been Islamic but their names have been changed are introduced with their names of the Islamic period, such as Bait-ul-Muqaddas, Askalon, Akbarabad, Qortoba, and Baneh Luqah instead of Jerusalem, Ashkelon, Agra, Cordoba, and Banjo Lukas.
- The names of the individuals that have undergone changes in the countries under the rule of former Soviet Union are mentioned in their original forms, such as Akhundzadeh instead of Akhundof. Regarding the persons who have a Hebrew as well as an Arabic name, or the persons who have a Latin name on the side of their Iranian or Islamic names, the original names are mentioned such as Ibn Disan, and Ibn Rushd instead of Bartizan and Averroes.
- In entering the Turkish, Mongolian, Hindi, Urdu and European words attempts have been made to enter them as they are pronounced in the original language and also their original composition is used in their writing.
- In entering the Greek names and words, their prevailing Islamic forms are used. For instance, Batlamius is used for Ptolemy and Anbazgholous for Empedocles.

- The names starting with the prefix “Abu”, “Ibn”, etc., when having other names, the other names are used to prevent excessive repletion, such as Abu Reyhan Biruni who is known also as Biruni and Ibn Babveyh who is known also as Sadduq.

- Regarding the terms prevalent in Persian and other languages (mainly Arabic and Turkish, etc.), often the one prevalent in Persian is used. Some of these terms are: badeh (wine), baardari (pregnancy), bazresi (inspection) – in Persian – instead of khamr, haml and taftish in Arabic word.

- Regarding the words composed of two or more parts, if the first part is a general term like science, port, sea, family (al) or general scientific concepts, the main part is selected as the entry and the first part of the composite word comes at its end; like: badi’, elm (figures of speech), “Siraf, Port”, “Azuf, Darya”, “Babveyh, Al”, “basit al-haqiqah, qaedeh”, instead of writing “elm badi”, “Port of Siraf”, “Sea of Azuf”, “al Babveyh”, and “qaedeh basit al-haqiqah”.

- Regarding the ruling dynasties, the suffix “an” is used like Samanian, Barmakian and Umavian.

- In the last two cases, there are some exceptions which stem from the fact that it is not possible to divide the names into two parts or some parts of the names are not well known such as Al-e Buyeh, Bahr Khazar (Caspian Sea), Bandar Anzali (Anzali Port), and Borhan Kholf.

- Brevity of selected form of entries – Regarding the names of the individuals, sometimes the family names or nicknames (if preferred) are used to distinguish them from other names. For instance, “Boroujerdi” is the surname of a number of scientists of the thirteenth and fourteenth centuries and hence in order to make a distinction between them their names are used as such: “Boroujerdi, Abdulrahim”, “Boroujerdi, Hajj Aqa Houssein”, and Boroujerdi, Asadullah”.

In arrangement of the entries, the prevailing rules and procedures of library catalogues are observed. For instance, “al” in Arabic (which means “the” in English) is not used in the beginning of the entry, rather the second “al” which comes in the beginning of the second word (like the one in Bahr al-Ulum) is taken into consideration. Regarding the letter hamzeh in Persian language the Persian letter "ي" is used, which is prevalent in today’s Persian language.

In some of the articles sometime reference is made to some issues that are the subject of an independent article in the Encyclopaedia. In order to prevent repetition, the related entries are determined in two ways. If the entry is mentioned in the text of the article, an asterisk is placed on its top left side. If the entry is not mentioned in the text of the article, it is referred to within brackets. For instance, in the article on “Batuiyan” the following words have been marked with asterisks: “sarai”, “Jangiz Khan” and “Ilkhanian”. Or in the article on “Baab”, reference has been made within brackets to (ensdad baab elm). Of course not all the entries appearing in the articles are marked with asterisks, rather the entries related to the same article are marked with asterisks to inform the reader about them. Therefore, such figures like Biruni, Ibn Sina (Avicenna) and Razi – about whom some articles will be written and whose names will appear frequently in other articles – are not marked with asterisks. Also sometime at the prerogative of the authors or editors, more relevant materials are referred to for more information of the readers. Hence, often such references are given at the end of the articles under the title “Additional reading”.