الْفِعْلُ (The Verb/Action)
The Arabic verb is a word which demonstrates the occurrence of something in time like: جَـاءَ ، يَجِئُ ، جِئْ. The time periods in which the verbs occur are three:
a) the past tense which shows that something has already happened;
b) the present tense which show the occurrence of something now;
c) the command tense which shows that an order has been given for action to be done immediately or in the near or distant future.
Among the signs of the verb are:
قَـدْ ، سَ ، سَـوْفَ ، تَـاءُ التأْنِـيث السَّكِنَةِ ، ضَمِيرُ الْفَاعِلُ ، نُونُ التَّوْكِيدِ
like when you say:
قَـدْ قَامَ ، قَـدْ يَقُومُ ، سَيَذْهَبُ ، سَوْفَ يَذْهَبُ ، قَامَتْ ، قُمْتُ ، قُمْتِ ، لَيَكْتُبَـنَّ ، لَيَكْتَبَْـنَ، اكْتُبَـنَّ ، اكْتَبْـنَ
الْـحَرْفُ (The Particle/Letter)
The particle like: هَـلْ ، فِـي ، لَـمْ ، عَـلى ، إِنَّ ، مِنْis a word which shows the meaning of another which follows it, but unlike the noun and verb, it does not have signs which distinguishes it.
الـْحُـرُوفُ (the particles) are divided between:
a) those which commonly govern both verbs and nouns, like حَـرْفَـا الاِسْـتِفْهَامِ (the two particles of interrogation) and حُـرُوفُ الْـعَطْفِ (the conjoining particles);
b) those particles which govern nouns exclusively, like حُرُوفُ الْـجَرِّ (the prepositions) and الْـحُـرُوفُ الْـمُشَـبَّهَةُ بِـاْلفِعْلِ (the particles which resemble the verb [that is to say إِنَّ وَ أَخْوَاتِـهَا -([ إِنَّ and its sisters]);
c) those particles which govern verbs exclusively, like حُـرُوفُ الشَّرْطِ (conditional particles), حُرُوفُ النَّصْبِ لِلْمُضَارِعِ (the particles that cause the present tense verb to be in the case of naṣb), and حُرُوفُ الْـجَزْمِ (the particles that cause the present tense verb to be in the case of jazm). All of these particles will be discussed in greater detail in the coming chapters.
Arabic Grammar – Preliminary Matters: Point 5 – الإِعْرَاب (Inflection) and الْبنَاء (The Fixed Construction)