The right to buy or sell property at an agreed price; the right is purchased and if it is not exercised by a stated date the money is forfeited WordNet 3.0 & Open English WordNet

An option contract, or simply option, is defined as "a promise which meets the requirements for the formation of a contract and limits the promisor's power to revoke an offer". Wikipedia

In finance, an option is a contract which conveys to its owner, the holder, the right, but not the obligation, to buy or sell a specific quantity of an underlying asset or instrument at a specified strike price on or before a specified date, depending on the style of the option. Wikipedia

A type of legal contract Wikipedia Disambiguation

An instrument that conveys the right, but not the obligation, to engage in a future transaction, or in a futures contract Wikipedia Disambiguation

Financial derivative conferring the right to to buy or sell a certain thing at a later date at an agreed price Wikidata

A contract giving the holder the right to buy or sell an asset at a set strike price; can apply to financial market transactions, or to ordinary transactions for tangible assets such as a residence or automobile. Wiktionary