UML22 — Section: 7.3.35

The modifications made for multiple languages (Issue 3391) could often be taken by the reader to mean that multiple languages may exist simultaneously in a single opaque expression. An example is the attribute "language:String[0..*] specifies the languages in which the expression is stated" could be interpreted to mean that the expression could be stated in mixed languages. Additionally plurality of verbs and modifying expressions often do not agree with the plurality of the sentence subject. An example of this is "The languages of an opaque expression, is specified, is often..." Subject is the sentence is "languages" so verb should be "are." Furthermore, this statement implies that a single ("an") opaque expression may have more than one language ("languages").

see above