قَامَ زَيْدٌ.
Translation: Zayd stood up.
Grammatical analysis
قَامَ: past-tense verb, built on fatḥa.
زَيْدٌ: subject (fāʿil), nominative with a visible ḍamma.
The verb requires a subject, so Zayd is nominative. Notice the ending of the word: زَيْدُ.