وَمَآ أَدْرَىٰكَ مَا يَوْمُ ٱلدِّينِ
Sentence structure
The first interrogative مَا is the topic and أَدْرَىٰكَ its predicate. The inner nominal clause مَا يَوْمُ ٱلدِّينِ supplies what is made known.
Ayah summary
The full terror of the Day of Recompense is beyond human comprehension.
وَمَآ — And what
Grammar: وَ resumes the discourse; interrogative مَا functions as the topic.
أَدْرَىٰكَ — can make you know
Grammar: A Form IV perfect verb. Its understood subject returns to the interrogative, attached كَ is the first object, and the following question supplies the second.
مَا — what
Grammar: An interrogative pronoun functioning as the topic of the inner nominal clause.
يَوْمُ — (is the) Day
Grammar: A nominative noun functioning as the predicate of the preceding interrogative مَا; it is also annexed to ٱلدِّينِ.
ٱلدِّينِ — (of) the Judgment
Grammar: A definite genitive noun functioning as the genitive complement of يَوْمُ.