Requirement
Requirements can come with different levels of specificity; for example , a requirement specification or requirement "spec" ( often imprecisely referred to as "the" spec/specs , but there are actually different sorts of specifications ) refers to an explicit , highly objective/clear ( and often quantitative ) requirement ( or sometimes , "set" of requirements ) to be satisfied by a material , design , product , or service . 
<triplet> specification <subj> Requirement <obj> subclass of