The Lanham Act[7] was intended to make “actionable the deceptive and misleading use of marks” and “to protect persons 768*768 engaged in . . . commerce against unfair competition.” § 45, 15 U. S. C. § 1127. Section 43(a) “prohibits a broader range of practices than does § 32,” which applies to registered marks, Inwood Laboratories, Inc. v. Ives Laboratories, Inc., 456 U. S. 844, 858 (1982), but it is common ground that § 43(a) protects qualifying unregistered trademarks and that the general principles qualifying a mark for registration under § 2 of the Lanham Act are for the most part applicable in determining whether an unregistered mark is entitled to protection under § 43(a). See A. J. Canfield Co. v. Honickman, 808 F. 2d 291, 299, n. 9 (CA3 1986); Thompson Medical Co. v. Pfizer Inc., 753 F. 2d 208, 215-216 (CA2 1985).
A trademark is defined in 15 U. S. C. § 1127 as including “any word, name, symbol, or device or any combination thereof” used by any person “to identify and distinguish his or her goods, including a unique product, from those manufactured or sold by others and to indicate the source of the goods, even if that source is unknown.” In order to be registered, a mark must be capable of distinguishing the applicant’s goods from those of others. § 1052. Marks are often classified in categories of generally increasing distinctiveness; following the classic formulation set out by Judge Friendly, they may be (1) generic; (2) descriptive; (3) suggestive; (4) arbitrary; or (5) fanciful. See Abercrombie & Fitch Co. v. Hunting World, Inc., 537 F. 2d 4, 9 (CA2 1976). The Court of Appeals followed this classification and petitioner accepts it. Brief for Petitioner 11-15. The latter three categories of marks, because their intrinsic nature serves to identify a particular source of a product, are deemed inherently distinctive and are entitled to protection. In contrast, generic marks—those that “refe[r] to the genus of which the particular product is a species,” Park `N Fly, Inc. v. Dollar Park & Fly, Inc., 469 U. S. 189, 194 (1985), citing Abercrombie & Fitch, supra, at 9—are not registrable as trademarks. Park `N Fly, supra, at 194.
769*769 Marks which are merely descriptive of a product are not inherently distinctive. When used to describe a product, they do not inherently identify a particular source, and hence cannot be protected. However, descriptive marks may acquire the distinctiveness which will allow them to be protected under the Act. Section 2 of the Lanham Act provides that a descriptive mark that otherwise could not be registered under the Act may be registered if it “has become distinctive of the applicant’s goods in commerce.” §§ 2(e), (f), 15 U. S. C. §§ 1052(e), (f). See Park `N Fly, supra, at 194, 196. This acquired distinctiveness is generally called “secondary meaning.” See ibid.; Inwood Laboratories, supra, at 851, n. 11; Kellogg Co. v. National Biscuit Co., 305 U. S. 111, 118 (1938). The concept of secondary meaning has been applied to actions under § 43(a). See, e. g., University of Georgia Athletic Assn. v. Laite, 756 F. 2d 1535 (CA11 1985); Thompson Medical Co. v. Pfizer Inc., supra.
The general rule regarding distinctiveness is clear: An identifying mark is distinctive and capable of being protected if it either (1) is inherently distinctive or (2) has acquired distinctiveness through secondary meaning. Restatement (Third) of Unfair Competition § 13, pp. 37-38, and Comment a (Tent. Draft No. 2, Mar. 23, 1990). Cf. Park `N Fly, supra, at 194. It is also clear that eligibility for protection under § 43(a) depends on nonfunctionality. See, e. g., Inwood Laboratories, supra, at 863 (White, J., concurring in result); see also, e. g., Brunswick Corp. v. Spinit Reel Co., 832 F. 2d 513, 517 (CA10 1987); First Brands Corp. v. Fred Meyers, Inc., 809 F. 2d 1378, 1381 (CA9 1987); Stormy Clime Ltd. v. ProGroup, Inc., 809 F. 2d 971, 974 (CA2 1987); Ambrit, Inc. v. Kraft, Inc., 812 F. 2d 1531, 1535 (CA11 1986); American Greetings Corp. v. Dan-Dee Imports, Inc., 807 F. 2d 1136, 1141 (CA3 1986). It is, of course, also undisputed that liability under § 43(a) requires proof of the likelihood of confusion. See, e. g., Brunswick Corp., supra, at 516-517; Ambrit, 770*770 supra, at 1535; First Brands, supra, at 1381; Stormy Clime, supra, at 974; American Greetings, supra, at 1141.