The Collaborative International Dictionary of English v.0.48:
Patency \Pa"ten*cy\, n. [See Patent.] 1. The condition of being open, enlarged, or spread. [1913 Webster] 2. The state of being patent or evident. [1913 Webster]WordNet (r) 3.0 (2006):
patency n 1: the openness (lack of obstruction) of a bodily passage or duct 2: the property of being easy to see and understand [syn: obviousness, noticeability, noticeableness, patency]