al-Salāmu ‘alaykum wa rahmatullāh,
One aspect of the miraculousness of the Qur'anic language lies in the precision of its words. As al-Suyuti said in al-Itqaan fee 'Uloom al-Qur'aan,
"It is possible to convey a single meaning with a variety of words, some more expressive than others. Likewise for the two parts – subject and predicate – of a sentence; each may be expressed in the most eloquent manner when taken alongside the other. Thus, it is necessary [in good composition] to consider the overall meaning of a sentence, then to consider every single word that may be used to convey that meaning, and then to use the most appropriate, expressive and eloquent of those words. This is impossible for man to do consistently, or even most of the time, but it is well within the Knowledge of Allaah [whose knowledge is boundless], and thus the Qur'an was considered the best and most eloquent of all speech…"
One example of this usage lies in the morphological forms found in the Qur'an, which will sometimes reflect the deeper meaning of the word itself, and upon reflection it can be found that not a single word in the Qur'an can be changed for another without it affecting the depth of meaning conveyed by the original word.
One example of this is in Yusuf, verse 23:
وَرَاوَدَتْهُ الَّتِي هُوَ فِي بَيْتِهَا عَن نَّفْسِهِ وَغَلَّقَتِ الأَبْوَابَ وَقَالَتْ هَيْتَ لَكَ
And she, in whose house he was, sought to seduce him. She closed the doors and said: "Come, you."
In this verse, Allaah used the verb form ghallaqa غلَّقَto mean 'closed'. Another form from the same root also means 'closed' – aghlaqa أغْلَقَ– yet there is a very eloquent reason for which Allaah used the previous form: the connotations of the pattern followed by the form ghallaqa are ones of repetitiveness and intensity of the action's performance, and thus the word form itself would give the reader who has knowledge of the Arabic language an idea of the intensity of the emotion and desire which drove the wife of al-'Azeez to rush around closing the doors of her house (some mufassiroon (exegetes) commented that there were seven doors that she closed, and hence the form also indicates the repetition of her going to door after door closing it) so she could quickly try to seduce Yusuf. None of this would have been reflected through the use of the alternative word form aghlaqa.
Another example of the same form reflecting repetition is in Surah Aal 'Imraan, verse 3,
نَزَّلَ عَلَيْكَ الْكِتَابَ بِالْحَقِّ مُصَدِّقاً لِّمَا بَيْنَ يَدَيْهِ وَأَنزَلَ التَّوْرَاةَ وَالإِنجِيلَ
It is He Who has sent down the Book (the Quran) to you (Muhammad SAW) with truth, confirming what came before it. And he sent down the Torah and the Gospel.
Although the English translation reflects no difference in the original words that were used to convey the meaning of 'sent down', a look at the Arabic will show us that the form nazzala نزَّلَwas used in reference to the Qur'an while the form anzala أَنْزَلَwas used in reference to the Torah and the Gospel. The reason for this goes back to the manner of revelation – the Qur'an was gradually revealed in a number of stages that spanned the 23 years of the Prophet Muhammad's (sallaa Allaahu 'alayhi wa sallam) Prophethood, as is reflected by the form nazzala which indicates repetition and grauality, while the Torah and the Gospel were revealed to the Prophets Musa (Moses) and 'Eesa (Jesus) at one time, as reflected by the form anzala.
This difference is more beautifully sealed when we look at the first verse of Surah al-Qadr,
إِنَّا أَنزَلْنَاهُ فِي لَيْلَةِ الْقَدْرِ
Verily! We have sent it (this Quran) down in the night of Al-Qadr (Decree)
In this verse, Allaah has used the verb anzala – which does not reflect graduality – to describe the revelation of the Qur'an, although He previously used nazzala! The reason for this is clear when the word is considered in it's context, as is explained by Ibn 'Abbas and others,
"Allah sent the Qur'an down all at one time from the Preserved Tablet to the House of Might (Bayt al-'Izzah), which is in the heaven of this world. Then it came down in parts to the Messenger of Allah based upon the incidents that occurred over a period of twenty-three years.''
Thus, it is clear that this verse is referring to Allaah sending the Qur'an down at one time to Bayt al-'Izzah on Laylat al-Qadr, and not to its gradual revelation to the Prophet; a concept so precisely and beautifully conveyed just through knowing the meaning of the forms used in the original Arabic.