Diplomacy is a key part of the game. Players — both human and AI — may trade technology, starbases, ships, planets and trade goods (unique improvements built by one race that provide a bonus to those obtaining them). Negotiation skill is an important factor which varies with inherent race bonuses and research; it can be possible to gain a significant technological advantage through careful trading with less sophisticated races.
Each race has customized text used during negotiation that signifies their current relations with the player. Relations depend on a number of factors, including current trade, relative ethical alignment, belligerance, military might and past actions. AI players may decide to initiate technology trades or demand tribute from the player, or to warn them of percieved threats.