UFUQ, khati kajest, ki qismi ba nazar namoyoni sathi zaminro ihota mekunad. Ufuqi namoyon barobari baland shudani joi mushohida vase meshavad va odatan az ufuqi haqiqi (matematiki) poyontar voqe megardad.
Ufuqi haqiqi doirai kalonest, ki az rui hamvorii ba khati shoquli (dar joi mushohida) perpendikulyar sferai osmonro meburad.