What do the single letters at the start of some surahs, such as “Alif Lam Mim”, mean?

They are abbreviations. Each letter stands for a word, and together they form a short statement about God. Alif Lam Mim, for example, means “I am Allah, the All-Knowing”.

A number of chapters of the Holy Qur’an begin with single letters that do not form an ordinary word. The best-known example is Alif Lam Mim at the start of the second chapter. Many readers wonder what these letters mean and how they should be translated.

A convincing explanation is that they are abbreviations. Each letter stands for a word. Alif Lam Mim is understood as “I am Allah, the All-Knowing”. So the letters are not empty signs. They are a condensed statement about God that introduces the chapter.

The verses above show how consistent this is. Where Alif Lam Ra appears, it is understood as “I am Allah, the All-Seeing”. Where Alif Lam Mim Ra appears, with both letters together, it means “I am Allah, the All-Knowing, the All-Seeing”. A letter carries the same meaning wherever it stands.

In this way God introduces Himself with one of His attributes right at the start of a chapter. From the very beginning the reader knows who is speaking to him. There are detailed treatises on these letters that deal with the subject thoroughly. Anyone interested will find much more there than a short answer can offer.