كَلَّا لَوْ تَعْلَمُونَ عِلْمَ ٱلْيَقِينِ ٥
Sentence structure
كَلَّا deters and لَوْ introduces a non-jussive condition. تَعْلَمُونَ is its plural imperfect verb. Accusative عِلْمَ reinforces the act of knowing and is annexed to genitive ٱلْيَقِينِ.
Ayah summary
Never so; had you known the Hereafter with certainty, you would not have remained heedless.
كَلَّا — No indeed
Grammar: A deterrent particle that rejects and warns.
لَوْ — if
Grammar: A non-jussive conditional particle.
تَعْلَمُونَ — you knew
Grammar: A second-person masculine-plural imperfect serving as the condition verb; واو الجماعة is subject.
عِلْمَ — with knowledge
Grammar: A masculine accusative cognate accusative reinforcing تَعْلَمُونَ; it is annexed to the next noun.
ٱلْيَقِينِ — of certainty
Grammar: A defined masculine genitive complement of عِلْمَ.