When the imperfect signal letter (the י, תּ, נ, or א prefix) is added, the characteristic ה prefix of the hif’il is lost, but in most cases it leaves a trace in the form of a patakh as the vowel under the signal letter. In general, the patakh under the signal letter is the most reliable way to recognize a hif’il imperfect or narrative verb. The exceptions are the פ”י paradigm, where the root י becomes a וֹ vowel letter, and empty ע roots, where the vowel under the signal letter is a kamatz.