لَيْتَ الطَّالِبَ حَاضِرٌ
Translation: If only the student were present.
«لَيْتَ»: wish particle; «الطَّالِبَ»: accusative ism; «حَاضِرٌ»: nominative khabar.
لَعَلَّ الْمَرِيضَ سَلِيمٌ
Translation: Perhaps the patient is well.
«لَعَلَّ»: particle of hope; «الْمَرِيضَ»: accusative ism; «سَلِيمٌ»: nominative khabar.
Wish expresses desire, while hope concerns a possible favourable outcome.