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Heterogram (classical compound: "different" + "written") is a term used mostly in the study of ancient texts for a special kind of a logogram consisting of the written representation of a word in a foreign language. In most cases, the two languages share the same script. However, while the word in the foreign language may be written either phonetically (representing the sounds of the foreign language) or logographically, in the borrowing language it is necessarily a logograph, since there is no relationship between the symbols used and the pronunciation of the word in the borrowing language.
In English, the written abbreviations e.g., i.e., and viz. are often read respectively as "for example", "that is", and "namely". When read this way, the abbreviations for the Latin words exempli gratia, id est, and videlicet are being used logographically to indicate unrelated English phrases. Similarly, the ampersand ⟨&⟩, originally a ligature for the Latin word et, in many European languages stands logographically for the local word for "and" regardless of pronunciation. This can be contrasted with the older way of abbreviating et cetera—&c.—where ⟨&⟩ is used to represent et as a full loanword, not a heterogram.
Heterograms are frequent in cuneiform scripts, such as the writing of Akkadian, which uses Sumerian heterograms. In Middle Iranian scripts derived from the Aramaic scripts (such as the Pahlavi scripts), all logograms are heterograms coming from Aramaic. Sometimes such heterograms are referred to by terms identifying the source language such as "Sumerograms" or "Aramaeograms".