Ideograms are specific signs and symbols that represent the word.  For example the picture of the sun represents "sun" or "day".  Ideograms are mostly used to depict objects and concrete concepts. 


For all the other words in the oral vocabulary that cannot be expressed through ideograms, phonograms are used.  Phonograms are the sounds that represent the word but has nothing to do with the word it depicts, they are a picture version of a homophone.  These are slightly more complex than the ideograms since it can represent a variable of one consonant or multiple sounds.

Here is a diagram demonstrates the difference between the categories in the rebus principle. 

Acrophonic Principle 

The Acrophonic principle is closely related to the rebus principle. The first sound of the word is represented by the picture that is used. 

Historical example

In the ancient Egypt in the 3rd millennium , the writing for the elites was hieroglyphs. Hieroglyphs was based on the Rebus principle.

In the decipherment of the Rosetta Stone, the Rebus principle was used to read the texts.  A basic example of the Rebus principle would be the reading the of names. The names are characterized by the "cartouche" that is shaped .

 This is an example of the name Cleopatra that was found encased in the cartouche in hieroglyphs on the Rosetta Stone. Each of the picture is based on a sound of the object. 

Here is the alphabet with the association of the object.