As discussed in the corresponding section in the introduction of this module, the task of defining what waste is implies a certain degree of subjectivity. ‪Thus, a first definition of waste is that material (solid, liquid or gas) generated by any human activity that is intended for abandonment, since for its owner it  represents nothing more than a nuisance.

However, the circumstance can arise that a product considered by a specific group of people to be waste because it represents a nuisance could be considered useful to another community or group. ‪Thus, the same substance, for economic or social circumstances, can be considered as waste or may have a useful value. ‪That is to say, products that in some societies are regarded as not useful can become objects of exchange with other utility in other societies, usually less developed than the first. ‪This would clarify the first definition, which could be the following: anything which the owner wants to discard or is required to discard, even if it is or may be useful or recoverable for another.

Consideration of any substance as waste, taking into account the owner, has been incorporated into the different laws governing waste and its management. ‪A clear example is the definition of waste that appears in Article 3 of Chapter I of Title I of Law 6/1993 of 15 July, of the Generalitat of Catalonia, regulating waste (as amended by Law 15/2003 of 13 June, regulating waste). ‪As is apparent in the Catalan law, "waste is understood as any substance or object that the owner discards or intends or is required to discard."