كَتَبْتُ رِسَالَةً لِأَخِي.
Meaning: I wrote a letter for my brother.
Kataba is a past verb; -tu is subject in the nominative position; risālatan is the accusative object; li- is a preposition; akhī is a genitive noun annexed to the speaker’s yāʾ, with a case ending understood before the suffix; -ī is the genitive possessive pronoun.
The six-noun overt letter-based markers do not apply when this noun is annexed to the speaker’s yāʾ.