A solution to a system of equations where all variables are non-zero. For example, outputs of all goods are positive, or all prices are positive. This is contrasted with a corner solution, in which some variables are zero. Statements of optimality conditions in terms of equality of marginal costs and marginal benefits are correct only for interior solutions.

• locomotive principle
• logarithm
• logarithmic scale
• logistic curve
• log-linear function
• log-normal distribution
• log-rolling
• Lomé Convention
• London Inter Bank Offered Rate
• London International Financial Futures and Options Exchange
• long-dated security
• long position
• long rate
• long run
• long-run average cost
• long-run marginal cost
• long-run Phillips curve
• long-term interest rate
• long-term unemployment
• Lorenz curve
• loss
• loss leader
• Louvre Accord
• loyalty, brand
• Ltd