In the Old Kingdom, this word was consistently masculine and usually distinct in its singular and plural forms. By the Middle Kingdom, its final consonant changed to t, with the consequence that the word changed genders to become feminine, and the singular was no longer typically distinguished in writing from its plural form. The written form from this time on occasionally included both the old and new consonants as rmṯt. Before the beginning of the New Kingdom, syllable-final t was lost throughout Egyptian, and in Late Egyptian the word returned to being masculine.
For many years Egyptologists distinguished this word as a masculine noun in its sense of ‘person’, etc., from a supposedly separate feminine collective term rmṯt(“people, humanity”); it is now clear the two words are one and the same, with the different written forms resulting from attempts to render the changing pronunciation (and gender) of the word as the final consonant first became t and then was elided entirely.
Inscriptions of the First Intermediate Period and Coffin Texts show a comprehensive collapse of the singular and plural written forms; from this point on they are no longer differentiated. By the start of the Middle Kingdom, the final consonant sound has changed from ṯ to t, and occasional writings reflecting this sound change begin to appear from the 12th Dynasty onward:
Post-Old Kingdom hieroglyphic writings of singular/plural rmṯ
By Late Egyptian, the final t is no longer pronounced in most circumstances; in situations where it is retained, such as when the word has an attached suffix pronoun, an additional t or tw is sometimes written at the end of the word to mark its retention.
“rmṯ (lemma ID 94530)”, in Thesaurus Linguae Aegyptiae, Corpus issue 17, Web app version 2.01, Tonio Sebastian Richter & Daniel A. Werning by order of the Berlin-Brandenburgische Akademie der Wissenschaften and Hans-Werner Fischer-Elfert & Peter Dils by order of the Sächsische Akademie der Wissenschaften zu Leipzig, 2004–15 December 2022
“rmṯ.t (lemma ID 94550)”, in Thesaurus Linguae Aegyptiae, Corpus issue 17, Web app version 2.01, Tonio Sebastian Richter & Daniel A. Werning by order of the Berlin-Brandenburgische Akademie der Wissenschaften and Hans-Werner Fischer-Elfert & Peter Dils by order of the Sächsische Akademie der Wissenschaften zu Leipzig, 2004–15 December 2022