The registered trademark symbol (®) is a symbol that provides notice that the preceding word or symbol is a trademark or service mark that has been registered with a national trademark office. A trademark is a symbol, word, or words legally registered or established by use as representing a company or product. In some countries it is against the law to use the registered trademark symbol for a mark that is not officially registered in any country.
Trademarks not officially registered can instead be marked with the trademark symbol ™, while unregistered service marks are marked with the service mark symbol ℠. The proper manner to display these symbols is immediately following the mark; the symbol is commonly in superscript style, but that is not legally required.
Because the ® symbol is not commonly available on typewriters (or ASCII), it is common to approximate it with the characters (R) (or (r)); for example the Python programming language Trademark Usage Policy advocates this usage. Example of legal equivalents are the phrase Registered, U.S. Patent and Trademark Office, which may be abbreviated to Reg U.S. Pat & TM Off., in the U.S., and the letters RTM in the UK.
The registered trademark character was added to several extended ASCII character sets, including ISO-8859-1 from which it was inherited by Unicode as U+00AE®REGISTERED SIGN (HTML ®·®). This is a different character from U+24C7ⓇCIRCLED LATIN CAPITAL LETTER R as many fonts draw the registered trademark symbol smaller and possibly superscripted.