Illā is interpreted in four ways:
One type of its use is as an exception; another type, although resembling an exception, actually marks the beginning of a new statement.
1. Illā is used in the sense of exception, as in the following verses:
On that Day, friends will be enemies to one another. (al-Zukhruf 43:67);
Then, making an exception among the friends, it is stated:
Except for the muttaqūn (those with taqwa, i.e., the God-conscious) {that is, the muttaqūn will not be enemies to one another}. (al-Zukhruf 43:67)
Those who do not invoke with Allah another deity or kill the soul which Allah has forbidden, except by right, and do not commit unlawful sexual intercourse. And whoever should do that will meet a penalty. (al-Furqān 25:68)
Then, making an exception, it is stated:
Except for those who repent, believe (have iman), and do righteous deeds {such a person will neither face punishment nor remain in the Fire}. (al-Furqān 25:70)
There are many similar verses.
2. Illā, while resembling an exception, does not actually serve as one but rather marks the start of a new statement or expression, as in the following verses:
Say, {O Prophet}: "I do not possess for myself any benefit or harm" {I can never do this!}. (al-Aʿrāf 7:188)
Here, the statement is completed, and then a new sentence begins, stating:
"Except what Allah wills" {surely, that [what Allah wills] will come to me}. (al-Aʿrāf 7:188)
Say: "I do not possess for myself any harm or benefit" {I can never do this}. (Yūnus 10:49)
The statement is completed here, and then a new sentence begins, stating:
"Except what Allah wills" {that [what Allah wills] will surely come to me}. Every nation has its [appointed] term {regarding punishment}. (Yūnus 10:49)
{Abraham said}: "I do not fear those you associate as partners with Him (shirk)." (al-Anʿām 6:80)
Then, a new sentence begins, stating:
"Except what my Lord wills" {what my Lord wills will come to me}. (al-Anʿām 6:80)
It is not for us to return to {i.e., the religion of shirk}. (al-Aʿrāf 7:89)
Then, a new sentence begins, stating:
Except if our Lord Allah wills {in that case, He would include/return us to it}. (al-Aʿrāf 7:89)
They will not taste death therein {ever}. (al-Dukhān 44:56) Then a new sentence begins, stating: Except the first death {they tasted in the world}. (al-Dukhān 44:56) No one has with him any favor for which a reward is due (i.e., with Abū Bakr, there is no favor of Bilāl for which Abū Bakr would have freed him in return; rather, Abū Bakr freed Bilāl to seek Allah's pleasure). (al-Layl 92:19)
Then, a new sentence begins, stating:
Except [illā] seeking the Face/pleasure of your Lord, the Most High. (al-Layl 92:20) You are only a reminder. You are not over them a tyrant. (al-Ghāshiya 88:21-22)
The statement is completed here, and then a new sentence begins, stating:
Except [illā] whoever turns away and disbelieves (commits kufr), Allah will punish him with the greatest punishment. (al-Ghāshiya 88:23-24)
We have certainly created man in the best of stature; Then We return him to the lowest of the low. (al-Tīn 95:4-5)
After the statement is completed, a new sentence begins, stating:
Except [illā] those who believe (have iman) and do righteous deeds; for them is a reward uninterrupted. (al-Tīn 95:6)
He is the Knower of the unseen {i.e., when the punishment will come}. But He does not disclose His unseen {i.e., the time of punishment} to anyone. (al-Jinn 72:26)
Then, a new sentence begins, stating:
Except [illā] a messenger whom He has approved. Indeed, He sends before each messenger and behind him observers. (al-Jinn 72:27)
Your wealth and your children will not bring you nearer to Us. (Sabaʾ 34:37)
Then, a new sentence begins, stating:
Except [illā] those who believe (have iman) and do righteous deeds, (it is these who are brought near to Allah). For them, their reward will be multiplied for what they did. (Sabaʾ 34:37)
3. Illā is used in the sense of giving information about something, as in the following verses:
There is nothing {that exists} (al-Ḥijr 15:21) Then, information about it is given:
But with Us are its treasures; [illā].
We do not send it down except according to a known measure. (al-Ḥijr 15:21)
You are nothing {other than this}, (Ibrāhīm 14:10)
Then, giving information about their state, it is said:
Except [illā] that you are men like us. (Ibrāhīm 14:10)
The messengers said to them: "We are nothing {other than this}," (Ibrāhīm 14:11)
Then, giving information about their state, they said:
"Except [illā] that we are men like you." (Ibrāhīm 14:11)
You are nothing {other than this}, (Yā-Sīn 36:47) Then, giving information, it is said:
Except [illā] that you are in clear error. (Yā-Sīn 36:47) There are many similar statements.
4. Illā is used in the sense of "other than" or "besides" (ghayr), as in the following verses:
If there had been in them [the heavens and the earth] gods other than [illā] Allah, they both would have been ruined. The Lord of the Throne is exalted above what they describe. (al-Anbiyāʾ 21:22)
If the truth had followed their desires, the heavens and the earth and whoever is in them would have been corrupted. (al-Muʾminūn 23:71)
The phrase Lā ilāha illā Allah also means bihi ghayrullāh [there is no deity other than Allah]. Similarly, all the expressions of Lā ilāha illā Allah in the Qur'an mean lā ilāha ghayrullāh [there is no deity other than Allah].