Pr (Gardiner sign listed no. O1) is the hieroglyph for 'house', the floor-plan of a walled building with an open doorway.
While its original pronunciation is not known with certainty, modern Egyptology assigns it the value of per, but purely on the basis of a convention specific to the discipline. However, the Ancient Greek rendering of the title pr-`3 as Greek, Ancient (to 1453);: φαραώ Greek, Ancient (to 1453);: pharaō suggests the reconstruction of the historical (Late Egyptian) pronunciation as *par, see Pharaoh#Etymology.
Pr combined with an associated "personal name", god, or location becomes the "house of .... ." An example for pharaoh Setnakhte is the city of: Pr-Atum, (city of Pithom). Pr and ankh-(life) is a "combination hieroglyph" and is the "word" for house of life. The "house of life" is a library for papyrus books-(scrolls), as well as a possible scriptorium.
The shape of pr in beginning dynasties had variations in the shape of a square, with the opening. See Garrett Reference for tomb of Official Ti.
Pr is one of hieroglyphs adopted into the Proto-Sinaitic script, the earliest known alphabetic writing system. It was used to represent the phoneme /b/ as in bayt, the Canaanite word for "house", after the hieroglyph's original meaning.[1] The Latin letter B is a distant descendant of this letter.