A function y = f(x) which has regular oscillations in y as x increases. The trigonometric functions y = cos (x) and y = sin (x) take this form, each fluctuating between an upper limit of +1 and a lower limit of -1 as x increases, with peaks and troughs at regular intervals of 2π. Any linear combination, such as y = acos (bx) + csin (dx) takes a similar oscillatory form, with different limits.

• immobile factors
• impact effect
• impatience
• imperfect competition
• imperialism, economic
• implicit contract
• implicit function
• importables
• import control
• import deposit
• Import Duties Act, 1932
• import duty
• imported inflation
• import levy
• import licence
• import penetration
• import propensity
• import quota
• import restriction
• imports
• import substitution
• import surcharge
• import tariff
• imputation system
• imputed charge for consumption of non-trading capital