What's the different between unit trust and mutual fund?

Actually the two terms are sometimes used interchangably rightly or wrongly. The term unit trust in the U K pretty much is interchangable with the term mutual fund in the U S.

There are however unit investment trusts in the U S that have a different meaning. These are pools of bonds and or stocks that are pooled together and sold to the public as a unit. They are unmanaged. Once they are sold, the interest and dividens are passed on to the investors and when the bonds come due, the priciple is paid back to the investors. The ones that hold stocks normally have a finite life span the end of which they are liquidated and the proceed distributed.

Mutual funds as commonly thought of in the U S are a managed collection of bonds and or equities that are sold to investors. Interest and dividends and capital gains are paid out each year to the investors if any. The managers buy and sells the investments as they see fit. They also collect a healthy fee for managing the mutual fund. Averages about 1.5% of assets annually.

a unit trust is a single entity
a mutual fund is a group of different entities

A trust unit is designed to give all of its profits to the shareholders
A mutual fund usually contains a basket of stocks which may pay some income to shareholders, but some may not.