A word may or may fall under a particular division of speech,because it is the function or the use that determines, which part of word it belong to in a given sentence
adverb:They wandered about in sheepskins and goat skins.
preposition:There is something pleasing about him.
adverb:The heavens are above.
preposition:The moral is above the civil.
adjective:Analyze the above sentence.
noun:Our blessings come from above.