This page is an alphabetical compilation of generic dialogue, lines which are repeated by many different NPCs. The dialogue options with any given NPC often depends on several different factors, such as location, faction membership, class, or race. Almost anything an NPC says to you will be recorded in your journal, indexed by topic.
Dialogue lines that are unique to a specific NPC are documented on that NPC's page. For a definitive list of named NPCs, see this page.