The articles of association of a company, often simply referred to as the articles (and then often capitalized as an abbreviation for the official name, which is a proper noun and usually contains the company name), are the regulations governing the relationships between the shareholders and directors of the company, and are a requirement for the establishment of a company under the law of the United Kingdom and many other countries. Together with the memorandum of association, they form the constitution of a company. The equivalent in the United States is Articles of incorporation.

Articles of association typically cover the issuing of shares (also called stock), the different voting and dividend rights attached to different classes of share, restrictions on the transfer of shares, the rules of board meetings and shareholder meetings, and other similar issues.

In the United Kingdom, model (and default) articles of association known as Table A have been published since 1865.[1] The articles of association of most companies – particularly small companies – are Table A, or closely derived from it. However, a company is free to incorporate under different articles of association, or to amend its articles of association at any time by a special resolution of its shareholders, provided that they meet the requirements and restrictions of the Companies Acts. Such requirements tend to be more onerous for public companies than for private ones.

The Companies Act 2006, which received Royal Assent on 8 November 2006 but will not be fully implemented until October 2009, provides for a new form of model articles of association for companies incorporated in the United Kingdom. Under the new legislation, the articles of association will become the single constitutional document for a UK company, and will subsume the role currently filled by the separate memorandum of association.

Here is what a few sources and bilingual documents say.

Hans Wehr and Al-Mawrid translate "النظام الأساسي" as statues.
Al-Mawrid translates "نظام الشركة الاساسي" as "articles of association".
Al-Mawrid translates "bylaw" as "القانون الداخلي".
Al-Mawrid translates "عقد تأسيس" as "articles of association"

www.websters-dictionary-online.org translates "النظام الأساسي للشركة" as "articles of association"

http://tra.ae/pdf/licences/Etisalat bilingual Final - REDACT... (Refer to Article 3.4.4)

Here, "النظام الأساسي" is translated as "bylaws",
and "عقد التأسيس" is translated as "articles of association".

http://www.mol.gov.jo/Portals/0/Arabic Glossary.pdf

Here, "النظام الداخلي" is translated as "bylaw".

Merriam Webster's : Bylaw: "a law, ordinance, or regulation made by a public or private corporation or an association or unincorporated society for the regulation of its own local or internal affairs and its dealings with others or for the government of its members"

Based on the above, these terms seem to be translated in different ways in different texts. I personally would use Bylaws for "النظام الأساسي للشركة" and Articles of Association for "عقد تأسيس" in texts dealing with companies/corporations.