An-Najm is interpreted in three ways:
1. An-Najm means kawkab (star); as in the following verses:
"It is the piercing star" {that is, a (bright) luminous star!} (al-Tāriq 86:3)
"And [He] has set up landmarks. And by the stars (najm) {that is, the stars} they are guided." (al-Naḥl 16:16)
"Then he cast a glance at the stars (nujūm) {that is, the stars}." (al-Ṣāffāt 37:88)
2. An-Najm is used in the sense of the nujūm (parts revealed in portions) of the Qur'an.
This is because the Qur'an was revealed to the Prophet (may Allah's blessings, peace, mercy, and blessings be upon him) in portions: as one verse, two verses, one surah, two surahs, and so on.
There are many verses in which [that is, where the word najm is used in the sense of "the portions of the Qur'an revealed in parts"]. As examples, we can mention the following verses:
"By the star (najm) when it descends" {that is, by each portion of the Qur'an revealed in parts}. (al-Najm 53:1)
The intent is that Jibril (peace be upon him) revealed the Qur'an to the Prophet (peace be upon him) in portions: as one verse, two verses, or one surah, two surahs, and more.
"But nay! I swear by the positions of the stars (nujūm) {that is, by the positions of the portions of the Qur'an which Jibril revealed to the Prophet in parts}..."
(al-Wāqiʿa 56:75)
Abu'l-ʿĀliya said:
"Learn the Qur'an five verses at a time, for the Prophet (peace be upon him) received it from Jibril five verses at a time."
Wakīʿ also relates from Ismāʿīl b. Khālid that he said:
"Abū ʿAbd al-Raḥmān al-Sulamī used to teach us the Qur'an five verses at a time."
3. The word an-Najm is used in the sense of a plant without a stem or trunk; as in the following verse:
"The najm {that is, plants without stems or trunks} and the shajar {that is, plants/trees with stems or trunks} prostrate/submit to Allah." (al-Raḥmān 55:6)