وهو إيراد المعنى الواحد في طرق مختلفة
It is the expression of one meaning through different methods.
Consider three illustrations:
Zayd is brave.
Zayd is as brave as a lion.
Zayd is a lion on the battlefield.
The central idea of courage is retained, while its presentation changes. Simile and figurative expression are examined systematically in bayan. For now, note the difference between choosing a form to suit the occasion and varying a meaning's presentation.