Pound cost average

In the UK, the regular investing of fixed amounts over regular periods, typically monthly, in order to accumulate holdings in securities such as shares, unit trusts and investment trusts.
When for example a unit trust price or investment trust price has fallen more units or shares can be purchased for that month. Similarly when the price rises then fewer units or shares can be purchased.
Over a period of a few years, the average price paid will be lower than the average share price for that period since more shares are bought at the lower price and fewer at the higher price.