An amount, usually expressed in percentage or decimal terms, applied as a proportionate amount per period, rather than per annum.
In relation to periodic yields (r):
r = R x days / year
r = periodic yield
R = nominal annual yield
days = actual number of days in the period under review
year = number of days in a conventional year
Interest is quoted at a market rate of 4% in USD, for 90 days maturity.
R = nominal annual yield = 0.04 (= 4%)
days = actual number of days in the period under review = 90
year = number of days in a conventional year = 360 for USD
Periodic yield = 0.04 x 90 / 360
= 0.01 (= 1%)
This is the periodic yield per 90 days in USD.