Spelled "trademark" in American English, as two words in England, Australia and Japan ("trade mark"), and with a hyphen ("trade-mark") in Canadian English.
Trademarks are a form of intellectual property and thus, monopolies granted by the Government and enforced by the Courts to traders or mechants reserving words, slogans, names or symbols (logos) or, in some jurisdictions, surnames (see below), sounds 
(jingles) or colors (Australia will even allow the trade-marking of a smell), that are used to mark and distinguish the merchant's goods or services from those of others.
Well-known trademarks include the Coca-Cola and McDonald's logos.
The trade-mark of the Victoria, British Columbia law firm of Duhaime Law is pictured.
In Caricline Ventures Ltd. v. ZZTY Holdings Ltd., a trade mark was defined as:
"(A) trade-mark must be used to distinguish a person's wares or services from those of others. A mark is not a trade-mark if it is not used for this purpose."
By way of further statements of the law on the topic, as it does not appear to be static in this area:
Justice Rouleau of the Federal Court of Canada in Philip Morris Inc. v. Imperial Tobacco Ltd.:
"... the very nature of a trade mark is to permit to distinguish the wares to which it is associated from others. One can also see that distinctiveness requires that three conditions be met: 1) that a mark and a product (or ware) be associated; 2) that the "owner" uses this association between the mark and his product and is manufacturing and selling his product; and, 3) that this association enables the owner of the mark to distinguish his product from that of others."
Chief Justice Fitzpatrick of the Supreme Court of Canada in Re Horlick:
"(A) surname is not necessarily incapable of being a registrable trade-mark." It may be registered for instance where it is as in this instance an uncommon name and its use has been so extensive that in fact it has become distinctive.
"Here the affidavits shew that the trade-mark has been in actual use and that such user has been sufficient to render it distinctive; food products in packages bearing as a conspicuous identifying feature the word 'Horlick' have been sold in the United States and in Great Britain and the Colonies for over forty years...."
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