A patent is the legal right of an inventor to exclude others from making or using a particular invention. This right is customarily limited in time, to 20 years from the date of the application submission in most countries.
(New Palgrave Dictionary of Economics, 2nd edition)
A trademark is a word, name, symbol, or device that is used in trade with goods to indicate the source of the goods and to distinguish them from the goods of others. Trademark rights may be used to prevent others from using a confusingly similar mark, but not to prevent others from making the same goods or from selling the same goods or services under a clearly different mark.
(U.S. Patent and Trademark Office)