When work is not protected by copyright, it’s said to be in the public domain.
Works may enter the public domain either it does not meet the requirements for copyright protection or its term of copyright protection has expired. Public domain works are not subject to the exclusive rights associated with copyright and thus can be freely copied, distributed, used in unoriginal works, publicly performed, and publicly shown by anyone without charge and without authorization.According to Deazley, if the institution of copyright necessitates permission before use, then the public domain allows for use without the need for permission. Clearly this would include works which, for whatever reason, fail to qualify as copyright protected in the first place. One category of such public domain works are those which pre date the establishment of the modern copyright framework, and consequently were never covered by any copyright protection. These works include myths and stories from antiquity, religious iconography and texts, and a multitude of other literary and artistic expressions that were produced after the invention of writing but before the formalization of the European copyright system, beginning during the 18th Century.
Other, more modern material can be in the public domain due to being outside of the scope of copyright law, if it does not satisfy the necessary requirements to attract copyright, such as that it is not an expression, or does not meet the threshold of originality required for protection. For example, a single word would not qualify as a literary work8 and therefore is not protectable by copyright. Likewise, copyright would not subsist in an un-original artistic work9. This category of public domain works is diverse and includes non-fixed expressions such as oral traditions and folk tales, common sayings and phrases, layperson knowledge, historical events, compendiums of facts, scientific discoveries, and other ideas that do not qualify for copyright protection (Samuelson, 2003: 151).