Domain spell

A cleric gets one domain spell slot for each spell level he can cast, starting at 1st level. When a cleric prepares a spell in a domain spell slot, it must come from one of his two domains. If a domain spell is not on the cleric spell list, a cleric can prepare it only in his domain spell slot.

NWN comparison

 * NWN domains only provided a few spells, not 1 spell at each spell level.
 * Domain spells in NWN could be prepared in any available spell slot of the correct level. There was no specific domain spell slot.