175. In post-Homeric Greek it is a rule (subject to a few exceptions only) that a preposition must either (1) enter into composition with a verb or (2) be followed immediately by and govern a noun or pronoun in an oblique case. But in the Homeric language the limitation of the prepositions to these twο uses is still far from being established. Α preposition may not only be separated from the case form which it governs (a licence sometimes found in later writers), but may stand as a distinct wοrd without governing any case. In other words, it may be placed in the sentence with the freedom of an adverb: e. g. ἀμφί may mean either on bοth sides (of an object expressed by an oblique case) or simply on both sides; ἐν may mean in (taking a dative), or simply inside; and so of the others.
γέλασσε δὲ πᾶσα περὶ χθών
all the earth smiled round about
ὑπαὶ δέ τε κόμπος ὀδόντων γίγνετο
beneath arose rattliπg of teeth
These uses, in which the preposition is treated as an ordinary Adverb of Place, may be called in general the adverbial uses.