Psi (Ѱ, ѱ) is a letter in the early Cyrillic alphabet, derived from the Greek letter psi (Ψ, ψ). It represents the sound /ps/, as in English naps. According to the school rules developed in the sixteenth and seventeenth centuries, such as Meletius Smotrytsky's grammar book, it was intended for use in words loaned from Greek—but it was occasionally used for writing native words, for example Ukrainian ѱы (psy, “dogs”).[1]