FINRA and the NYSE define a Pattern Day Trader (PDT) as one who effects four or more day trades (same day opening and closing of a given equity security (“stock”) or equity option) within a five business day period.A day trade is defined as a purchase and sale of a security (US and Non-US) within the same trading day.  The FINRA and NYSE instituted regulations intended to limit the amount of trading that can be done in accounts with small amounts of capital, specifically accounts with less than 25,000 USD Net Liquidation Value.  A Pattern Day Trader is someone who effects 4 or more day trades within a 5 business day period.