There are differing conventions for transliterating Sumerian, Akkadian (Babylonian), and Hittite (and Luwian) cuneiform texts. One convention that sees wide use across the different fields is the use of acute and grave accents as an abbreviation for homophone disambiguation. Thus, "u" is equivalent to "u1", the first glyph expressing phonetic "u". An acute accent, "ú", is equivalent to the second, "u2", and a grave accent "ù" to the third, "u3" glyph in the series (while the sequence of numbering is conventional but essentially arbitrary and subject to the history of decipherment). In Sumerian transliteration, a multiplication sign 'x' is used to indicate typographic ligatures. As shown above, signs "as such" are represented in capital letters, while the specific reading selected in the transliteration is represented in small letters. Thus, capital letters can be used to indicate a so-called Diri compound – a sign sequence that has, in combination, a reading different from the sum of the individual constituent signs (for example, the compound IGI.A – "eye" + "water" – has the reading "imhur", meaning "foam"). In a Diri compound, the individual signs are separated with dots in transliteration. Capital letters may also be used to indicate a Sumerogram (for example, KÙ.BABBAR – Sumerian for "silver" – being used with the intended Akkadian reading "kaspum", "silver"), an Akkadogram, or simply a sign sequence of whose reading the editor is uncertain. Naturally, the "real" reading, if it is clear, will be presented in small letters in the transliteration: IGI.A will be rendered as imhur4.