Given the task definition and input, reply with output. In this task, we ask you to elaborate the sentence without changing its general meaning. You can do so by explaining further the input sentence, using more precise wording, adding qualifiers and auxiliary information etc.

The main tengwar letters are placed into four vertical series ( " te ́ mar " ) and six horizontal rows ( " tyeller " ) .

These principal letters are divided into four series ( " te ́ mar " ) that correspond to the main places of articulation and into six grades ( " tyeller " ) that correspond to the main manners of articulation .