Copyright protects intellectual property fixed in tangible form, such as a book, video or painting. Thus, a quote can only be copyrighted if it is fixed in one of these forms. Copyright is automatic for all items published after 1978. You do not need to register the item with the U.S. Copyright Office or put a copyright notice on the item to receive copyright protection. However, to sue for a copyright violation, your item must be registered with the U.S. Copyright Office; you may register the item and sue even after the violation has taken place.
Fair Use Exception
The fair use doctrine poses a major hurdle to the copyright of quotations. Copyrighted items may be excerpted for scholarly and educational purposes. For example, a reviewer may publish a quote from a book in a review. The law provides no specific guidelines about how long a republished quote must be to constitute copyright infringement. If your quotation is a long one, you will have a better chance of enforcing the copyright.
To copyright your quotation, it must be in a fixed medium, such as a book or video. You may then assert your copyright immediately. You may register copyrights on the U.S. Copyright Office web page by providing information about the copyrighted item and paying a fee.
If the quotation you wish to protect is short and you intend to use it in commerce -- such as for a business motto or similar use -- trademark protection may be a better alternative. Trademarks protect unique marks used in commerce, so incorporating your quotation as a part of your business logo or name may offer it protection from being reused for profit by other businesses. However, others will still be permitted to quote the line.