The length of time it takes an oscillatory function to return to any given point in its cycle. The functions y = acos x or z = bsin x have a period of oscillation of 2π; if the cycle reaches a given point, such as its peak, at time t₀, it returns to the same point at times t = t₀ + 2π, t = t₀ + 4π, etc. If the oscillatory function takes the form y = acos cx or z = bsin cx, the period of oscillation will be 2π/c, and the cycle returns to the same point as it was at t₀ whenever 2π/c or any integer multiple of it is added to t₀.

• Public Sector Borrowing Requirement
• public sector debt
• Public Sector Debt Repayment
• public spending
• public utility
• public works
• pump priming
• punishment strategy
• purchase tax
• purchasing power
• purchasing power parity
• pure floating exchange rate
• put option
• pyramid scheme
• q, Tobin's
• quadrant
• quadratic
• qualification of accounts
• quality control
• quality ladder
• quality standards
• quango
• quantity and price adjustment
• quantity demanded
• quantity discount