… is from page 17 of the 2010 Liberty Fund edition of Israel Kirzner’s important 1966 volume, An Essay on Capital  (footnote excluded):
The market process consists in the systematic chain of events that ensues from the interaction in the market of the decisions of numerous participants. These decision-makers find, at the outset, that the opportunities that are in fact being offered to them in the market (by virtue of the decisions of others) are different (either more or less attractive) than those originally expected. From the lessons learned in the market in this way, there follows a systematic pattern of adjustment and revision in the decisions made by market participants. This pattern of adjustment constitutes the market process.