Learn Turkish: Güneş, büyük bir yıldızdır.

This is the factual suffix you are learning in this lesson. Normally, you do not always need a suffix to say 'is' in Turkish. However, when you are stating a universal fact, a scientific truth, or a definition like 'The sun is a star', you attach -dır to the end to sound formal and objective.

Why is the word order büyük bir yıldızdır instead of bir büyük yıldızdır?

In English, we say 'a large star', putting 'a' first. In Turkish, when you use an adjective with the indefinite article bir, the adjective usually comes first. The pattern is 'Adjective + bir + Noun', which literally translates as 'large a star'.

Why is there a comma right after Güneş?

In Turkish, commas are frequently used right after the subject of a sentence to clearly separate it from the rest of the information. This is a standard punctuation rule that highlights exactly what the sentence is about.

Why does the factual suffix take the form -dır and not -tır or -dir here?

The exact spelling of the suffix depends on the word it attaches to. The last vowel in yıldız is an undotted 'ı', so vowel harmony dictates the suffix must also use 'ı'. Also, because yıldız ends in 'z' (which is a voiced consonant), the suffix starts with 'd' instead of the harder 't'.