As far as my schooling goes "soon" is an adverb and has many guises
1. Within a short period after this or that time, event, etc.:
"We shall know soon after Des knows"
2. Before long; in the near future; at an early date:
"Des will soon have no more clue than we have"
3. Promptly or quickly:
"You"ll soon be having a laugh"
4. Readily or willingly:
"We will know as soon as Des buys a drink"
5. Early in a period of time; before the time specified is much advanced:
"Soon in the year"
have a nice day