Yield is one division: a year of dividends divided by today's share price. Because the price changes daily, the dividend yield you see quoted is a snapshot of this morning, not a promise about next year.
Once you own the share, yield on cost is usually the more honest number — it compares the dividend to what you actually paid. A rising price lowers the quoted yield and leaves your yield on cost untouched. For a share you're only considering, forward yield — what the company pays now, scaled to a year — is the figure the screener shows.
Price rises to £40 and the yield reads 3.0% — the company changed nothing.
Educational content only. It is not personal financial advice.