Sentence:  The purpose of this provision was thus explained in the Court 's opinion : `` Section 7 is designed to arrest in its incipiency not only the substantial lessening of competition from the acquisition by one corporation of the whole or any part of the stock of a competing corporation , but also to arrest in their incipiency restraints or <WSD>monopolies</WSD> in a relevant market which , as a reasonable probability , appear at the time of suit likely to result from the acquisition by one corporation of all or any part of the stock of any other corporation . 
Meaning of the word marked with <WSD> tags:  (economics) a market in which there are many buyers but only one seller