Çавахла функци (çавахла куçарав) — аргумента хăй патнех куçаракан функци. Урăхла каласан, аргумент мĕнле, функцийĕ те çаплах. Ĕнтĕ вара, функцишĕн ку çапла çырăнать: f(x) = x мĕнпур аргументшăн.
Mapa, Sadhan Kumar (7 April 2014). Higher Algebra Abstract and Linear (11th ed.). Sarat Book House. p. 36. ISBN 978-93-80663-24-1.
Proceedings of Symposia in Pure Mathematics. American Mathematical Society. 1974. p. 92. ISBN 978-0-8218-1425-3. ...then the diagonal set determined by M is the identity relation...
Rosales, J. C.; García-Sánchez, P. A. (1999). Finitely Generated Commutative Monoids. Nova Publishers. p. 1. ISBN 978-1-56072-670-8. The element 0 is usually referred to as the identity element and if it exists, it is unique