Mā is interpreted in seven ways:
1. Mā, (with the same meaning as the negative particle): it is used in the sense of 'lā'; as in the following verses:
Say, "I do not ask you [mā (that is, lā as'alukum)] for any payment for it [min-ajrin], and I am not one of those who fabricate." [mā (that is, lā anā mina'l-mutatakallifīn)] (that is, I am not among those who ask you to give payment [ajran]). (Ṣād 38:86)
It is not said to you [mā (that is, lā) yuqālu laka]. (Fussilat 41:43)
They eat nothing in their bellies except fire [mā (that is, lā) ya'kulūna]. (al-Baqara 2:174)
It is not for any human being [mā kāna—it is not/it cannot be, (that is, lā yanbaghī=it does not befit/is not appropriate)] that Allah should give him the Scripture, authority, and prophethood and then he would say to the people, "Be servants to me rather than Allah." (Āl ʿImrān 3:79)
It is not for any human being [mā kāna=it is not/it cannot be (that is, lā yanbaghī=it does not befit/is not appropriate)]... (al-Shūrā 42:51)
2. Mā is used in the sense of 'laysa' / 'there is not'; as in the following verses:
And to Thamūd [We sent] their brother Ṣāliḥ. He said, "O my people! Worship Allah; you have no deity other than Him (that is, there is not for you [laysa lakum] any Lord besides Him)." (Hūd 11:61)
And to Madyan [We sent] their brother Shuʿayb. He said, "O my people! Worship Allah; you have no deity other than Him [mā lakum] (that is, there is not for you [laysa lakum] any Lord besides Him)." (Hūd 11:84)
3. Mā is used in the sense of 'alladhī' [that which/those things which]; as in the following verses:
By that which created [mā khalaqa] the male and the female {that is, He who created [alladhī khalaqa] the male and the female}. (al-Layl 92:3)
Did there not come to them that which was not given [mā lam ya'ti {that is, alladhī lam ya'ti}] to their forefathers? (al-Muʾminūn 23:68)
Indeed, those who conceal that which We sent down [mā anzalnā {that is, alladhī anzalnā}] of clear proofs... (al-Baqara 2:159)
Say, "That which I ask of you [mā sa'altukum {that is, alladhī sa'altukum}] of payment; it is for you." (Sabaʾ 34:47)
He made for you from the ships and the cattle that which you ride [mā tarkabūn (that is, alladhī tarkabūn)]. (al-Zukhruf 43:12)
There are many similar statements.
4. The particle mā is used as an interrogative in the sense of 'ayy' [which thing, what?]; as in the following verses:
{He said to his sons, Yaʿqūb}: "What will you worship [mā {that is, ayy shay'}] after me?" (al-Baqara 2:133)
What is it that makes them {i.e., the Jews} patient in the face of the Fire [mā {that is, ayy shay'}] {that is, what is their recompense for an action that leads them to the Fire / what is it that makes them endure it}?! (al-Baqara 2:175)
Woe to man! What makes him deny [mā {that is, ayy shay'}]?! (ʿAbasa 80:17)
5. Mā is used as 'lam' [the negative particle that comes before the imperfect verb]; as in the following verses:
By Allah, our Lord, we were not of those who associated partners [mā kunnā mushrikīn] {that is, lam nakun mushrikīn: we were not among those who committed shirk}. (al-Anʿām 6:23)
We were not [mā kunnā] {that is, lam nakun: we were not} absent. (al-Aʿrāf 7:7)
We did not destroy those towns {that is, lam nakun muhlikī'l-qurā: We did not destroy those towns}; except that their people were wrongdoers. (al-Qaṣaṣ 28:59)
There are many similar statements.
6. Mā, in speech, is sometimes a 'ṣila' [connecting particle with no independent meaning]—which has no specific principle in Qur'anic exegesis—as in the following verses:
Indeed, Allah is not shy to present an example—even that of a mosquito [mā baʿūḍatan]. (al-Baqara 2:26)
The mā particle in the phrase is an extra connector (ṣila) with no independent meaning.
It was by a mercy from Allah that you were gentle with them. (Āl ʿImrān 3:159)
The mā particle in the verse is a connector in the phrase; thus, the expression fa-bi-mā raḥmatan min-Allāh means fa-bi raḥmatan min-Allāh.
But for their breaking of the covenant... (al-Nisāʾ 4:155)
The mā particle in the verse is a connector in the phrase; thus, the expression fa-bi-mā naqḍihim mīthāqahum means fa-bi naqḍihim mīthāqahum.
After a little while... (al-Muʾminūn 23:40)
The mā particle in the verse is a connector in the phrase; thus, the expression 'ammā qalīlin means 'an qalīlin.
7. Mā is used in the sense of the comparative particle 'kamā' [like, as]; as in the following verses:
So that you may warn a people whose forefathers were not warned. (Yā-Sīn 36:6)
Here, the phrase mā undhira ābāʾuhum [their forefathers were not warned] means kamā undhira ābāʾuhum [as their forefathers were warned].
The wretched will be in the Fire. Therein they will have [from it] a [violent] exhaling and inhaling... Abiding therein as long as the heavens and the earth endure (that is, just as the heavens and the earth endure for the people of the world and those therein cannot leave}... (Hūd 11:106-107)
That is, the people of the Fire will remain alive therein/there in the Fire forever; they will never die. The Fire will never be cut off from them. The exception in the phrase, except what your Lord wills, in the verse is for those among the people of tawhid (the oneness of God) who have entered the Fire. They will not remain in the Fire with those who abide forever; they will be taken out of the Fire/Hell to be sent to Paradise.
But the blessed will be in Paradise. Abiding therein as long as the heavens and the earth endure, except what your Lord wills. (Hūd 11:108)
That is, just as the heavens and the earth endure for the people of the world and those therein cannot leave, so too Paradise will be everlasting for the people of Paradise. The people of Paradise will never die; Paradise will never come to an end. The exception in the phrase, except what your Lord wills, is for those among the people of tawhid who are taken out of Hell and admitted to Paradise later, and thus were initially left out.