In short

English sorts words into eight or nine parts of speech. Arabic sorts every word in the language into exactly three: اسْم (noun), فِعْل (verb) and حَرْف (particle). There is no separate class for adjectives, no class for pronouns, none for demonstratives, and none for most adverbs - in Arabic terms all of those are اسْم. Three boxes, and every word goes into one of them. You choose the box by a grammatical test, not by what the word means.

The second half of the lesson is about the little vowel that sits on the last letter. It is not decoration and it is not part of the word’s spelling: it is a job label. On a noun that final vowel says which case the noun is in - that is, what job it is doing in the sentence. On a verb the same three vowels say something completely different: mood, not case. On a particle there is no label at all, because a particle never changes. At this stage your task is only to recognise these endings when they are printed. You are not yet expected to produce them.

The rule

One word, one class - decided by test. Do not ask “what does this word mean?” Ask “what can this word do?” مَريضٌ (“ill”) feels like an adjective to an English speaker, but it takes tanwīn, takes الـ (المَريضُ) and can follow a preposition (عَنِ المَريضِ), so it is an اسْم. Meaning did not decide; behaviour did.

Test 1 - does it take الـ? Only an اسْم can. الكِتابُ، البَيْتُ، الجَديدُ، المَدْرَسَةُ are all nouns. A verb never takes الـ; a particle never takes الـ. If you can prefix the article, you have a noun and you can stop testing.

Test 2 - does it take tanwīn (ـٌ ـً ـٍ)? Only an اسْم can: كِتابٌ، وَلَدًا، بَيْتٍ. Tanwīn is the indefinite mark; verbs never carry it, and neither does any particle you will meet at this level. (Lesson 4 shows that a noun never carries الـ and tanwīn at the same time.)

Test 3 - can it follow a preposition? Whatever comes directly after مِنْ، في، عَلى، إِلى، عَنْ is an اسْم - or, later on, a whole clause standing in for one (lesson 34). في البَيْتِ، مِنَ المَدينَةِ، عَلى الطّاوِلَةِ. This test is the one that catches nouns which fail tests 1 and 2 - see the note on fixed words below.

الاسْم carries case. A noun in a fully vocalized text normally ends in one of three vowels, and that vowel tells you its job: ـُ for the doer, ـَ for the object, ـِ after a preposition. Arabic grammar calls this إِعْراب. English shows the same distinction only on pronouns (he / him), Arabic shows it on every noun.

الفِعْل carries tense and person, and its final vowel is mood, not case. كَتَبَ (“he wrote”) and يَكْتُبُ (“he writes”) are verbs: they say when and who. They refuse الـ and refuse tanwīn. The ـُ on يَكْتُبُ is real and you must print it, but it does not mean “nominative”. It is the default mood ending, and it changes to ـَ or to a sukūn when certain particles come in front of the verb - لَمْ يَكْتُبْ، أَنْ يَكْتُبَ. Those are lessons 33 and 35; here just register that a verb’s last vowel belongs to a different system.

الحَرْف is invariable and means nothing on its own. مِنْ، في، عَلى، إِلى، هَلْ، لا، وَ، أَنْ never take an ending of their own; the most they do is swap a final sukūn for a helping vowel when the next word opens with الـ (مِنَ البَيْتِ). Say مِنْ out loud and you have said nothing - “from” what? A particle only does its work when it is attached to something else. The class is a small closed list of a few dozen words, so you can genuinely learn it; اسْم and فِعْل are open classes with hundreds of thousands of members.

Parse a sentence, word by word. Take ذَهَبَ الوَلَدُ إِلى المَدْرَسَةِ (“the boy went to school”). Four words, three classes: ذَهَبَ is a فِعْل (tense and person, no الـ), الوَلَدُ is an اسْم (it has الـ) ending in ـُ because it is the doer, إِلى is a حَرْف (fixed, meaningless alone), and المَدْرَسَةِ is an اسْم ending in ـِ because it follows a preposition. Every Arabic sentence you will ever read decomposes exactly like this.

The case trio, on one noun. Keep the noun and change its job, and only the last vowel moves: ذَهَبَ الوَلَدُ (he is the one going) - رَأَيْتُ الوَلَدَ (he is what I saw) - نَظَرْتُ إِلى الوَلَدِ (he comes after a preposition). Same three consonants, three different endings, three different jobs. That is the whole idea of إِعْراب in one line.

Recognise, do not produce. For now: when you read a vocalized text, notice the ending and let it tell you who did what. When you speak, you may stop before the ending - pausing on the bare word is what native speakers do at the end of a sentence anyway - that is the pausal form, in the pronunciation guide. The full system, with all its sub-markers, is lesson 40. Nothing between here and there asks you to case-mark spontaneously.

Adjectives, pronouns and demonstratives are all nouns. الجَديدُ (“the new one”) takes الـ and case -> اسْم. هُوَ، أَنا، أَنْتَ can stand as the subject and can follow a preposition (مِنْهُ) -> اسْم. هٰذا، هٰذِهِ point at things and behave like nouns -> اسْم. Time and place words such as اليَوْمَ، غَدًا، أَمامَ، تَحْتَ are nouns too, standing in the ـَ case (lesson 31). If you are tempted to invent a fourth class for any of these, resist: Arabic has three.

مَبْنِيّ: the words with a frozen ending. A مُعْرَب word changes its final vowel with its job (الكِتابُ / الكِتابَ / الكِتابِ). A مَبْنِيّ word is fixed - it keeps one shape everywhere. Every حَرْف is مَبْنِيّ, the past-tense verb is مَبْنِيّ (ذَهَبَ ends in ـَ in every sentence), and a small set of nouns is مَبْنِيّ too: the pronouns, the demonstratives, الَّذي. That is why هٰذا and هُوَ fail tests 1 and 2 and are still nouns - test 3 catches them.

And all of it is invisible in real text. Newspapers, novels and websites print almost no vowel marks: ذهب الولد إلى المدرسة. The endings are still grammatically there and an educated reader supplies them, but nothing on the page shows them. This path prints full تَشْكيل precisely so that you can see the grammar you are being taught; do not expect the outside world to be so generous (reading bare text is its own lesson in the pronunciation guide).

Forms & patterns

The three-way test. One “yes” in the first three rows settles the class immediately.

A sentence parsed word by word: ذَهَبَ الوَلَدُ إِلى المَدْرَسَةِ.

The case trio on one noun - recognition only; the full inventory is lesson 40.

The same three vowels on a verb are a different system. Do not read these as cases.

Fixed (مَبْنِيّ) or variable (مُعْرَب)?

The particles you already need. This is a closed list; a dozen of them carry most of your early reading. The prepositions are covered properly in lesson 16.

Examples

Common mistakes

• الطّالِبُ الْيَدْرُسُ -> الطّالِبُ يَدْرُسُ - a verb can never take الـ. To say “the student who studies” you need a relative clause (lesson 39), not an article glued to a verb.
• يَكْتُبٌ -> يَكْتُبُ - tanwīn belongs to nouns only. No verb in Arabic ever ends in ـٌ ـً ـٍ.
• لَمْ يَكْتُبُ -> لَمْ يَكْتُبْ - the last vowel of a verb is mood, not case, so a particle in front of it can cut it to a sukūn. A noun’s ending would never react to لَمْ.
• ذَهَبَ الوَلَدَ إِلى المَدْرَسَةِ. -> ذَهَبَ الوَلَدُ إِلى المَدْرَسَةِ. - the doer takes ـُ. With ـَ you have said that someone went the boy, which is nonsense.
• إِلى المَدْرَسَةُ -> إِلى المَدْرَسَةِ - whatever follows a preposition is a noun in the ـِ case. (A small class of nouns writes that same case with ـَ instead - إِلى مِصْرَ - but that is lesson 41; everything you meet now takes ـِ.)
• مِنْ هٰذا الكِتابُ -> مِنْ هٰذا الكِتابِ - هٰذا is a noun, not a particle; it sits after مِنْ as a fixed (مَبْنِيّ) form, and the noun that follows still has to show the ـِ.
• الرِّسالَةُ مِنْ هُوَ. -> الرِّسالَةُ مِنْهُ. - pronouns are nouns and can follow a preposition, but the attached form is used there, never the standalone one (lesson 7).
• هَلْ أَنْتَ طالِبًا؟ -> هَلْ أَنْتَ طالِبٌ؟ - هَلْ is a حَرْف: it adds a question and touches no ending. The predicate of a nominal sentence stays as it was (lesson 2).
• ذَهَبْتُ إِلى. -> ذَهَبْتُ إِلى المَدْرَسَةِ. - a particle cannot end a sentence, because it means nothing by itself. إِلى must be followed by its noun.

Tips

• Run the الـ test first. It is one second of thought and it separates nouns from everything else faster than any other question.
• Two vowels, two questions. On a noun the final vowel answers “what job?”; on a verb it answers “what mood?”. Never let a verb’s ـُ tempt you into calling it a subject.
• Memory hook: name, act, glue. اسْم names a thing, فِعْل acts, حَرْف glues the other two together and does nothing on its own.
• Learn the particles as vocabulary, not as grammar. There are only a few dozen and you meet the same twelve constantly; every other word you will ever meet is a noun or a verb.
• Stop translating English word classes. “Adjective”, “pronoun”, “adverb” and “article” have no Arabic box of their own - filing them under اسْم removes about half of the confusion at A1.
• Read case endings aloud when you read a vocalized text, and drop them when you speak spontaneously. Recognition now, production much later (lesson 40).
• Do not panic about unvocalized text. The endings are invisible there, and word order plus context carry you; this path prints them so you can watch the machinery work.
• When a sentence confuses you, parse it like the table above: class, then reason, then ending. Four columns and the fog usually lifts.