This etymology implies the same etymon σέλας as the competing etymology (see σελήνη / σέλας + νέον), but instead of understanding the moon as the "glowing one", it understands it as the "glowing not". This either simply means that the moon shines much less than the sun because it is not firelike ((σέλας was used for the sun and for fire)), or implies some scientific knowledge of the nature of the moon, which gets its glow from the sun and is deprived of an internal source of light. This scientific fact is then mapped onto the word and a different etymology invented to agree with it. From the formal point of view, this etymology is explicitly given as one of three exceptions to the rule that a privative prefix is always prefixed and never suffixed (never at the end of the word). This explanation with a suffixed νη- is already found in Orion for χελώνη (see χελώνη / κέλλω), but not for σελήνη. The privative prefix νη- is a creation of Greek and not an inherited morpheme, and as the regular privative prefix ἀ- of which it is a variant, it is never found at the end of a word. The principle of assuming that a prefix can become a postfix, that is, appear at the end of the word, may be based on the use of prepositions in anastrophe in prepositional phrases in poetry: compare one of the etymologies provided for καρδία as κῆρ + διά.