Rights & Warrants
Both let the holder buy the issuer's stock at a set price: preemptive rights are short-term (weeks), issued to existing shareholders, and priced below the market; warrants are long-term (often years), usually attached to other securities as a sweetener, and priced above the market at issuance.
A rights offering lets shareholders maintain their proportionate ownership when new shares are issued — the preemptive right in action. Warrants have value only if the stock eventually rises above the exercise price, making them a speculative, leveraged play on the issuer.