The difference being that you might one day see a unicorn.
A liquidity trap requires
1. Low nominal interest rates. (The nominal interest rate is the interest rate as stated.)
2. High real interest rates, due to low or negative inflation.* (The real interest rate is the nominal interest rate minus the rate of expected inflation. If the nominal interest rate is 5 percent and the expected inflation rate is 2 percent, then the real interest rate is 3 percent.)
3. No way for the monetary authority to escape from (1) and (2). Hence the term trap.
(*In this post, Paul Krugman surprises me by stating implying (as far as I can tell) that high real interest rates are a sign that we are not in a liquidity trap. That is completely the opposite of my understanding.
Kling must be assuming away the possibility that the IS curve has shifted inwards. But isn’t the message here that the demand for investment has fallen and/or the national savings schedule has risen so much that even with very low interest rates, investment would not equal national savings at full employment?