Omission can have several distinct aims:
1. قَصْدُ الِاخْتِصَارِ — delivering a known point economically.
2. احْتِرَازٌ عَنِ الْعَبَثِ — avoiding repetition of an already evident predicate, as in «زَيْدٌ مُنْطَلِقٌ وَعَمْرٌو».
3. ضِيقُ الْمَقَامِ — the occasion or poetic metre gives little room for length, provided clarity survives.
4. اتِّبَاعُ الِاسْتِعْمَالِ — following an established Arabic construction, including concise expressions of sudden encounter.
Correct analysis first identifies the omitted meaning through a contextual clue, then explains which rhetorical purpose the omission serves here. A short but unintelligible expression is not eloquent merely because it uses fewer words.