1. the quality or state of being double or twofold in nature, form, or character
Usage: formal or literary; rare in modern usage
2. deceitfulness or double-dealing; the practice of saying one thing and meaning another
Usage: archaic or obsolete usage; 'duplicity' is the standard modern term

Examples

• The duplexity of the crystal structure made it valuable for optical applications.
• His duplexity in the negotiations—claiming friendship while plotting against us—was eventually exposed.
• The philosopher explored the duplexity of human nature: reason and emotion in constant tension.
• She was troubled by the duplexity of his promises; his actions never matched his words.
• The duplexity of the building's design allowed it to serve two distinct purposes.
• Medieval theologians debated the duplexity of Christ's nature, divine and human.