NIM stands for Net Interest Margin.
In a mortgage context, NIM is a key financial metric used by banks to measure the difference between the interest income they earn from loans and the interest they pay to depositors, relative to their total interest-earning assets.
NIM is expressed as a percentage and gauges the efficiency and profitability of a bank's lending activities. Essentially, a higher NIM indicates a bank is earning a greater amount from its lending, relative to what it pays for funds.