Accusative Particle (إنّ) · حرف مشبه بالفعلإِنَّ means 'indeed' and carries the doubling shaddah ـّ; it pushes its own topic into the accusative — the ending usually shown by a fathah ـَ, a small slanted stroke above the final letter — while the comment about that topic stays in the nominative, the ending usually shown by a ḍammah ـُ, a small curl above the final letter. Here its topic is the attached هُمْ 'they', which it takes as its accusative subject — a pronoun keeps one fixed shape, so no fathah appears, but the role it fills is the accusative one: 'indeed they…'. L15 · R3

Attached Pronoun · ضمير متصلAn attached pronoun is a mini-word glued onto another word. The ending هُمْ on إِنَّهُمْ is such a suffix, standing for 'they' — the topic that إِنَّ takes as its subject. L3 · R6

Detached Pronoun · ضمير منفصلA detached pronoun is a standalone word for 'they', 'you', 'I', and the like. هُمُ is the standalone word 'they', placed between 'indeed they' and 'the corrupters' to fasten the two together. L3 · R2

Subject (Mubtada') · مبتدأThe subject is a noun a sentence talks about — its topic — and it stands in the nominative, the 'topic form' usually shown by a ḍammah ـُ, a small curl written above the final letter. هُمُ 'they' stands as this topic — a pronoun keeps one fixed shape, so no ḍammah appears, but the role it fills is the nominative one — and what follows, 'the corrupters', is what is said about them: it is they who are the corrupters. L6 · R2

Definite Article · أل التعريفThe prefix ٱلْ at the front of a noun means 'the' — one specific, known group. Here it marks مُفْسِدُونَ as 'the corrupters', the known group who spread ruin. L2 · R9

Noun · اسمA word that accepts the prefix ٱلْ ('the') is a noun — a naming word. This word carries that prefix and names a group — the corrupters — from the root فسد, to spread corruption and cause ruin. L1 · R1

Masculine Noun · اسم مذكرArabic treats every naming word as grammatically 'he' or 'she'. This word carries no feminine marker such as a ة at its end, so it falls to the default and is treated as 'he': a masculine noun. L2 · R3

Plural Noun · جمعA plural noun refers to three or more. The masculine sound plural in the nominative adds the ending ـُونَ. مُفْسِدُونَ ends in ـُونَ, so it names the many corrupters, not just one. L2 · R6

Nominative · مرفوعThe nominative is the ending a naming word takes when it completes what is said about the topic; for this kind of plural that ending is ـُونَ. ٱلْمُفْسِدُونَ carries that ـُونَ ending in its own right, as the comment about 'they': they are the corrupters. L2 · R10

Predicate (Khabar) · خبرThe predicate is the part that tells you something about the topic, in the nominative ending. The topic was هُمُ 'they'; ٱلْمُفْسِدُونَ is what is said about them — the corrupters — standing nominative in its own right. L6 · R3

Active Participle · اسم فاعلAn active participle is a naming word built from a verb's root to name the one who does the action. Built from the root فسد (to spread corruption), ٱلْمُفْسِدُونَ names the doers — those who work corruption, 'the corrupters'. L11 · R3

Supplementary Particle · حرف زائدA supplementary particle is an extra word added for weight, whose removal would not change the core meaning. The prefix وَ here rides along with 'but', adding to the flow without altering the sense. L14 · R4

Retraction Particle (بَلْ / لَٰكِن) · حرف إضراب واستدراكA retraction particle like لَٰكِن 'but' adjusts or qualifies what was just said, steering the sentence in a new direction. Here لَٰكِن turns from stating that they are the corrupters to noting what they fail to grasp: 'but they perceive it not'. L20 · R18

Particle · حرفA particle is a small helper word with no meaning standing alone; it takes no ending and does not name or act. لَّا is such a helper word here. L1 · R8

Negation Particle · حرف نفيA negation particle is a word meaning 'not'. لَّا negates the present-tense verb after it: 'they do not perceive' the corruption they work. L4 · R5

Verb · فعلA verb is a word for an action tied to a time. يَشْعُرُونَ names an action — perceiving, realizing — from the root شعر, to perceive and be aware. L1 · R7

Present Tense Verb · فعل مضارعA present tense verb describes ongoing action and opens with one of the four prefixes أ ن ي ت. يَشْعُرُونَ opens with يَ; with لَّا before it, it means 'they do not perceive'. L8 · R3

The Five Verbs · الأفعال الخمسةThe Five Verbs are the five present shapes ending in نَ, one being يَفْعَلُونَ 'they do'. يَشْعُرُونَ has that ونَ ending marking 'they', and its kept نَ shows it stands in its plain mood after the simple negation لَّا. L10 · R10

Attached Pronoun · ضمير متصلAn attached pronoun is a mini-word glued onto another word. The ونَ ending on يَشْعُرُونَ is such a suffix, standing for 'they' — the ones who do not perceive. L3 · R6

Doer (Fa'il) · فاعلThe doer is the one performing the action, so it stands in the nominative — the 'subject form', usually shown by a ḍammah ـُ, a small curl written above the final letter. The ونَ ending on يَشْعُرُونَ is that doer, 'they' — the ones who do not perceive; on this attached pronoun the shape is fixed, so no ḍammah appears, but the role it fills is the nominative one. L9 · R4