Sun letters, moon letters, and the article al-
Learning to read Arabic aloud means knowing when the lam of the definite article ال (al-) is pronounced and when it vanishes into the next consonant. This split between 14 sun letters and 14 moon letters is one of the first pronunciation rules students meet. This tool classifies every word you enter so you can see the pattern.
The two complete sets
| Sun letters (الحروف الشمسية) | Moon letters (الحروف القمرية) |
|---|---|
| ت ث د ذ ر ز س ش ص ض ط ظ ل ن | أ ب ج ح خ ع غ ف ق ك م هـ و ي |
The 14 sun letters are largely the coronal consonants — sounds articulated with the blade of the tongue at or near the same point of contact used for lam itself. Because lam and the following sun letter share a place of articulation, the lam assimilates to the next sound: saying “al-shams” would require the tongue to briefly leave that position and return, so natural speech glides directly from the alif to a doubled sheen: ash-shams.
The 14 moon letters are articulated far enough from the lam’s position that no assimilation occurs — the lam is pronounced clearly: al-qamar.
How it works
The rule depends entirely on the first letter of the noun the article attaches to. The tool strips diacritics, skips a leading ال, and tests the next consonant:
الشمس -> first letter ش (sheen) -> sun -> pronounced "ash-shams"
القمر -> first letter ق (qaf) -> moon -> pronounced "al-qamar"Sun-letter words are highlighted warm; moon-letter words cool.
How assimilation appears in written Arabic
The spelling of the alif-lam article never changes — ال is always written in full regardless of whether the following letter is a sun or moon letter. The assimilation is only a pronunciation rule. In fully vocalised text, the distinction is shown by:
- A sukūn (ْ) on the lam of ال when the next letter is a moon letter, marking that the lam is pronounced without a following vowel
- No vowel on the lam and a shadda (ّ) on the sun letter when the word starts with a sun letter, marking that it is doubled
This is one reason beginners reading Quran can be confused by the written text:
seeing الشَّمْس in a mushaf, the lam appears without a vowel mark and the sheen
has a shadda — visual cues that the assimilation has happened, even though the
alif-lam is still written.
Practical use for students
When studying Arabic vocabulary, the sun/moon classification of a word’s first letter is worth learning alongside the word itself. You will be reading ال before almost every Arabic noun when it is definite, and knowing immediately whether to say ash- or al- before it is a core fluency habit. Paste a vocabulary list into this checker to see which pattern each word follows at a glance.