Psalm 145:1–21 is a so-called acrostic. This means that the first word of line 1 starts with the letter a; subsequently, every sentence, every part, or every stanza thereafter starts with the following letter of the alphabet. The Hebrew alphabet consists of twenty-two letters and this psalm has only twenty-one verses. That is, because the sentence with the letter n (the fourteenth letter) is missing.

However, as you can see in some English and Dutch translations, the fixed metre, of each verse consisting of two lines, is broken up in Psalm 145:13, where it has four lines instead. The reason for this is that a psalm scroll has been found in the caves by the Dead Sea, and that does have a sentence which starts with the Hebrew letter n. And that line is then included in the translation in Psalm 145:13 (or Psalm 145:14).