market efficiency means degree to which market prices shows. if market is efficient there is no under valuation and overvaluation of price of shares and securities.The test of weakness of market efficiency whether a time series kof stock returns has zero autocorrelation.there are 3 theories undesr the market efficiency.

1. weak

2.semi strong

3.strong

In finance, the efficient market hypothesis asserts that finanial market are informationally effiient ,the weak form shows that the prices of shares already reflect all available information,.

under semi stronge form shows all publicaly available information and that prices and change to reflect new informations.

under strong form shows the price already hidden or insider information .