In mathematics, modular units are certain units of rings of integers of fields of modular functions, introduced by Kubert and Lang (1975). They are functions whose zeroes and poles are confined to the cusps (images of infinity).
See also Cyclotomic unit Elliptic unit
References Kubert, Daniel S.; Lang, Serge (1981), Modular units, Grundlehren der Mathematischen Wissenschaften [Fundamental Principles of Mathematical Science], vol. 244, Berlin, New York: Springer-Verlag, ISBN 978-0-387-90517-4, MR 0648603, Zbl 0492.12002 Kubert, Daniel S.; Lang, Serge (1975), "Units in the modular function field. I", Mathematische Annalen, 218 (1): 67–96, doi:10.1007/BF01350068, ISSN 0025-5831, MR 0437496, Zbl 0311.14005