The number of phonograms is very restricted, but some signs have all these powers.
Flexional consonants are almost always marked by phonograms, except in very early times; as when the feminine word z.t, cobra, is spelled ~ Also, if a sign had more than one value, a phonogram would be added to indicate which of its values was intended:
This practice had the advantage also of distinguishing determinatives from phonograms. Thus the root or syllable un is regularly written ~ ~to avoid confusion with the detcrminative~.
Biliteral phonograms are very rare as phonetic complements, nor are two biliteral phonograms employed together in writing the radicals of a word.
It is noteworthy that though words were so freely spelled in alphabetic characters, especially in the time of the Old Kingdom, no advance was ever made towards excluding the cumbersome word-signs and biliteral phonograms, which, by a judicious use of determinatives, might well have been rendered quite superfluous.
Thus signs, according to their employment, are said to be (I) wordsigns, (2) phonograms, or (3) determinatives.
Phonograms.Only a limited number of signs are found with this use, but they are of the greatest importance.
By searching throughout the whole mass of normal inscriptions, earlier than the periods of Greek and Roman rule when great liberties were taken with the writing, probably no more than one hundred different phonograms can be found.
As Egyptian roots seldom exceeded three letters, there was no need for triliteral phonograms to spell them.
Determinatives.Most signs can on occasion be used as determinatives, but those that are very commonly employed as phonograms or as secondary word-signs are seldom employed as determinatives; and when they are so used they are often somewhat differentiated.
Some few signs ideographic of a group of ideas are made to express particular words belonging to that group by the aid of phonograms which point out the special meaning.