Rule 1: 1. The vocabulary of associations and committees
The officers of a body are its رَئِيسٌ chairman, president (feminine رَئِيسَةٌ), its نَائِبُ الرَّئِيسِ vice-chairman, its سِكْرِتِيرٌ or أَمِينُ السِّرِّ secretary and its أَمِينُ الصُّنْدُوقِ treasurer, literally the trustee of the fund. They are chosen by the Form VIII verb اِنْتَخَبَ، يَنْتَخِبُ to elect (verbal noun اِنْتِخَابٌ, plural اِنْتِخَابَاتٌ elections). The office held stands in the accusative after the verb and its object, or after the passive: اِنْتَخَبُوهُ رَئِيسًا they elected him chairman, اُنْتُخِبَتْ نَائِبَةً لِلرَّئِيسِ she was elected vice-chairman. A meeting يُعْقَدُ is held (literally is tied), and it is بِرِئَاسَةِ فُلَانٍ under so-and-so's chairmanship.
عُقِدَ اجْتِمَاعٌ عَامٌّ لِأَعْضَاءِ الْجَمْعِيَّةِ بِرِئَاسَةِ الدُّكْتُورِ سَمِيرٍ.
ʿuqida jtimāʿun ʿāmmun li-aʿḍāʾi l-jamʿiyyati bi-riʾāsati d-duktūri samīrin
A general meeting of the society's members was held under the chairmanship of Dr Samīr.
عُقِدَ: passive of عَقَدَ 'to tie'; the subject اِجْتِمَاعٌ follows.
اِنْتَخَبَ الْأَعْضَاءُ السَّيِّدَةَ لَيْلَى أَمِينَةً لِلصُّنْدُوقِ.
intakhaba l-aʿḍāʾu s-sayyidata laylā amīnatan li-ṣ-ṣundūqi
The members elected Mrs Laylā treasurer.
Object السَّيِّدَةَ, then the office أَمِينَةً in the accusative.
اُنْتُخِبَ أَخِي عُضْوًا فِي لَجْنَةِ الْمَسْجِدِ.
untukhiba akhī ʿuḍwan fī lajnati l-masjidi
My brother was elected a member of the mosque committee.
Passive اُنْتُخِبَ; the office عُضْوًا stays accusative.
لِلْجَمْعِيَّةِ عِشْرُونَ فَرْعًا فِي الْمُدُنِ وَالْقُرَى.
li-l-jamʿiyyati ʿishrūna farʿan fi l-muduni wa-l-qurā
The society has twenty branches in the towns and villages.
After 20 the counted noun is an accusative singular.
أَقَامَتِ اللَّجْنَةُ حَفْلَةً بِمُنَاسَبَةِ مُرُورِ عَشْرِ سَنَوَاتٍ عَلَى تَأْسِيسِهَا.
aqāmati l-lajnatu ḥaflatan bi-munāsabati murūri ʿashri sanawātin ʿalā taʾsīsihā
The committee held a celebration on the occasion of ten years since its founding.
مُرُورُ … عَلَى 'the passing of … since', literally 'over'.