This article is from the FAQ, by with numerous contributions by others.
The net asset value (NAV) is the value of the fund's underlying
securities. It is calculated at the end of the trading day.
Any open-end fund buy or sell order received on that day is traded
based on the net asset value calculated at the end of the day.
A few funds calculate net asset value at more frequent intervals
and process trades at those values.
 
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