In metaphor, an expression is transferred to another meaning on the basis of resemblance, with contextual indication excluding its ordinary literal reference. Tajrīd instead imagines a second bearer drawn from the original in order to heighten possession of a quality.
Examples:
“Fulān baḥr fī al-jūd” — the metaphorical use of “sea” for great generosity stands out.
“Laʾin saʾalta fulānan la-tasʾalanna bihi al-baḥr” — a related image becomes an extraction of a sea-like counterpart from the man.
An expression may involve metaphor and tajrīd at different analytical levels. Their names do not explain precisely the same mechanism.