Recently I have seen several examples of people using the word “post” instead of the word “after.” In the dictionary, “post” is listed either as a noun, a verb or a prefix that is attached to a word without a hyphen.
Noun: post office, fence post, trading post
Verb: post a guard, post a job opening, post the news on my blog
Prefix: postseason, postdate, postgame, postmortem, postscript
Note that it means “after” only when attached to the front of another word, not as a separate word.
The temperature of the cement increases for several hours post completion.
In such a case, the preposition “after” is correct. The whole purpose of a preposition is to describe a relationship (before, on, toward, over), and the word “after” serves that role.
“Post” as a standalone word is not a preposition.