Stock split and reverse split
A stock split divides each share into several, multiplying the number of shares and reducing the price in the same proportion. A reverse split does the opposite: it consolidates several shares into one and raises the price. Neither changes the value of the holding or of the company. They matter for what they break: any historical series or per-share figure not adjusted for splits produces meaningless comparisons, and an EPS from ten years ago left uncorrected can be wrong by a factor of four.
See also
See it on real data
Celsmar computes this from the accounts companies file with their regulator, and shows which line every figure comes from. Free to start, no card.
Definition for informational purposes. It is not financial advice nor a recommendation to buy or sell.