وَيَنْوِي لِلصَّلَاةِ الَّتِي يَدْخُلُ فِيهَا بِنِيَّةٍ لَا يَفْصِلُ بَيْنَهَا وَبَيْنَ التَّحْرِيمَةِ بِعَمَلٍ
Translation: He intends the prayer he is entering, with an intention not separated from the opening takbir by an intervening act.
Niyyah is the inward resolve specifying the prayer; tahrimah is the opening takbir entering prayer.
In the Hanafi approach, intention need not be verbalized simultaneously with takbir. An intention formed shortly beforehand remains valid if no intervening act severs its relation to the opening.