Conjunction and Disjunction/al-wasl was-fasl الوصل والفص
Conjunction الوصل literally: to join two things. Rhetorically: to bring two statements or propositions together by connecting them with the particle (و). For example: the students are studying and the teachers are praying الطلاب يدرسون والمدرسون يصلون where the two statements “الطلاب يدرسون” and “المدرسون يصلون” are brought together and connected through the conjunction particle (و). Disjunction الفصل is when conjunction does not occur, i.e. when two statements are not connected. For example: Zaid is studying. ‘Amp is playing زيد يدرس. عمرو يلعب where we have two independent statements that are not connected by the particle (و).
Conjunction الوصل between two sentences is required in the following cases: a) both sentences share a grammatical ruling for example: The hard working student used to read and write كان الطالب المجد يقرأ ويكتب where the two verbal sentences يقرأ and يكتب are connected as they share the same grammatical rule of being in the place of نصب خبر كان. b) both sentences agree in the sense that both are reporting statements for example: the boys are standing and the girls are sitting الأولاد واقفون والبنات جالسات. c) both sentences agree in the sense that both are informing statements for example: Study and memorize your lesson! ادرس واحفظ درسك! d) If the sentences disagree in the sense that one is reporting statement and the other is informing and if they were disconnected, then the meaning may not be obvious or may not be obvious that both are connected for example: Zaid arrived and he is happy جاء زيد وهو سعيد where the two statements are connected in meaning, hence, conjunctions is rhetorically preferred and applied.
Disjunction الفصل occurs in the following cases: a) When both sentences are unified in the sense that one is بدل or توكيد or صفة from the other for example: Zaid is a hardworking intelligent student زيد طالب مجتهد ذكي where the two adjectives ذكي and مجتهد do not required conjunction as they are grammatically unified. (توكيد، بدل) b) when both sentences are in contrast, i.e. they disagree in being reporting or informing or there is no relation between the two for example: Pray! The success of an servant is depends on praying صل، نجاح العبد متوقف على أداء الصلوات c) if the second sentence serves as an answer to a question imposed or understood from the first sentence. If you ask them about me, they know me! إذا سألتهم عني يعرفوني where the second statement is an answer to the first.