In Arabic and Maltese, consonants are divided into two groups: the sun/solar letters (Arabic: حروف شمسية ḥurūf shamsiyyah, Maltese: konsonanti xemxin) and moon/lunar letters (حروف قمرية ḥurūf qamariyyah, Maltese: konsonanti qamrin).

In those languages, all nouns start with the word "al" (الـ) in Arabic or "il" in Maltese. Both words mean "the." If a sun letter comes after the consonant, the "l" sound in "al" or "il" is dropped and is replaced by whatever sound the letter makes. However, if a moon letter comes after, the "l" sound in those words stays.

In Arabic, the word for "the sun" is ash-shams because the "sh" sound is a sun letter. Meanwhile, the word for "the moon" is al-qamar because the "q" sound is a moon letter.

Below is a chart of the sun and moon letters in Arabic.

The ال 'al-' is written down in Arabic regardless of how it is pronounced. In the case of sun letters, a mark called the shaddah (ـّـ) is written over the sun letter. For moon letters, a mark called the sukun (ـْـ)is written over the letter ل lam in the al-.

Below is a chart of the sun and moon letters in Maltese.

If a word starts with any of the moon letters, the word il- stays the same. However, if it stats with a sun letter, the word il-changes to iċ-, id-, in-, ir-, is-, it-, ix-, iż-, iz-.

If a word begins with two consonants, it changes to "l-i-." For example, skola (school) becomes l-iskola (the school).^[1]