Rule 1: 1. Formation of Form IV
Perfect أَفْعَلَ: أَرْسَلَ he sent. Imperfect يُفْعِلُ: يُرْسِلُ, with ḍamma on the prefix (the mark of Forms II, III and IV) and kasra before the last radical. Imperative أَفْعِلْ: أَرْسِلْ. The endings are those of every verb you know, so the only new things are the hamza and the sukūn on the first radical. Compare Form I يَخْرُجُ he goes out with Form IV يُخْرِجُ he takes out: the vowels alone carry the difference.
أَرْسَلَتِ الْأُمُّ ابْنَهَا إِلَى السُّوقِ.
arsalati l-ummu bnahā ila s-sūqi
The mother sent her son to the market.
يُدْخِلُ الْخَادِمُ الضُّيُوفَ إِلَى الْمَجْلِسِ.
yudkhilu l-khādimu ḍ-ḍuyūfa ila l-majlisi
The servant shows the guests into the sitting room.
أَخْرِجِ الْكَرَاسِيَّ إِلَى الْحَدِيقَةِ!
akhriji l-karāsiyya ila l-ḥadīqati
Take the chairs out into the garden!
Imperative أَخْرِجْ; the sukūn becomes kasra before the article. The hamza is pronounced.
لَمْ يُغْلِقْ أَحَدٌ بَابَ الْمَخْزَنِ.
lam yughliq aḥadun bāba l-makhzani
Nobody closed the storeroom door.
Jussive of أَغْلَقَ, the verb behind مُغْلَقٌ 'closed' of lesson 23.
أُرِيدُ أَنْ أُشْعِلَ الْمِصْبَاحَ.
urīdu an ushʿila l-miṣbāḥa
I want to light the lamp.
First person أُشْعِلُ, subjunctive أُشْعِلَ.