A stock's share price divided by its earnings per share — the most common shorthand for whether a stock looks 'expensive' or 'cheap'.
The P/E ratio tells you how many rupees investors are willing to pay for every one rupee of a company's current annual profit. A P/E of 25 means the market is valuing the stock at 25 times its earnings. Higher P/E generally reflects higher expected future growth (or, sometimes, overvaluation); lower P/E can mean the stock is undervalued, or that the market expects earnings to decline.
P/E is only meaningful when compared — against the company's own historical average, against direct sector peers, or against the broader index. A P/E of 40 might be cheap for a fast-growing tech company and expensive for a slow-growing utility.