Rules of Lam

The letter Lam has two well-known rulings in Quranic recitation that every reciter must master: the rules of the definite article "Al-", and the rules of the Lam in the word "Allah" (Lafz al-Jalalah).

First: Rules of the Definite Article "Al-"

The definite article Lam is the extra Lam that attaches to indefinite nouns to make them definite, as in: الشمس (the sun), القمر (the moon). It has two states when pronounced:

Its fourteen letters are remembered by the first letters of this line:

طِبْ ثُمَّ صِل رَحِمًا تَفُزْ ضِفْ ذَا نِعَمْ   دَعْ سُوءَ ظَنٍّ زُرْ شَريفًا لِلْكَرَمْ

They are: t, th, s, r, t, d, dh, n, d, s, z, z, sh, l

﴾ الطَّامَّةُ ﴿ (An-Naba') — ﴾ الرَّحْمَنُ ﴿ (Ar-Rahman)
﴾ الشَّمْسُ ﴿ (Ash-Shams) — ﴾ الدِينِ ﴿ (Al-Fatiha)

Its fourteen letters are remembered by the phrase "Ibghi Hajjaka Wakhaf 'Aqeemah":

{a, b, gh, h, j, k, w, kh, f, ' (ayn), q, y, m, h}

﴾ الْحَمْدُ ﴿ (Al-Fatiha) — ﴾ الْكِتَابُ ﴿ (Al-Baqarah)
﴾ الْقَمَرِ ﴿ (Al-Qamar) — ﴾ الْعَالَمِينَ ﴿ (Al-Fatiha)

How to Tell Them Apart in the Mushaf

The two can be distinguished simply by looking at how the word is written in the noble Mushaf: the Solar Lam is written without a visible sukoon mark, and the letter following it carries a shaddah (doubling mark). The Lunar Lam, on the other hand, is written with a visible sukoon mark, and there is no shaddah on the following letter.

Second: Rules of the Lam in the Word "Allah"

The word "Allah" (Lafz al-Jalalah) has two pronunciations of its Lam — heavy (tafkheem) or light (tarqeeq) — depending on the vowel that precedes it.

﴾ قَالَ اللَّهُ ﴿ (after fatha) — ﴾ نَصْرُ اللَّهِ ﴿ (after damma)
﴾ هُوَ اللَّهُ أَحَدً ﴿ (Al-Ikhlas: 1)

﴾ بِسْمِ اللَّهِ ﴿ (Al-Fatiha: 1) — ﴾ قُلْ هُوَ اللَّهُ أَحَدً ﴿
﴾ فِي اللَّهِ ﴿ — ﴾ مِنَ اللَّهِ ﴿

A Note Worth Remembering

This ruling is specific to the word "Allah" and does not extend to other occurrences of Lam in speech. The rule is simple: look at the vowel immediately before the Lam — if it is a kasra, pronounce it light; if it is a fatha or damma, pronounce it heavy.