“nth-generation language” is a buzzword. It is a marketing term. There is no universally accepted definition of what exactly defines the “nth generation” for n > 2. Some people categorize “scripting” languages such as Perl or Python as 4GLs because they are much more high-level than C, while others think the defining characteristics of 4GLs is that they're domain-specific, e.g. SQL. Some nitwits even think that Java (a mid-90s language full of object orientation and garbage collection and reflection) belongs in the same “3GL” category as Fortran (from the 50s) and C (from the 70s).
A categorization so confused such as “4th generation language” is of no use. You may see it in old textbooks, or hear it from people that started programming in the 80s, but a tag such as “4GL” is worthless without an accompanying explanation of what exactly the author means by that.
Since no one immediately understands what you mean by “4GL”, you should not use such categorizations. Instead, use specific terms to communicate precisely what you mean. E.g. all of NASM, LLVM IR, and Jasmin are assembly languages, but the latter two target VMs, and the last one is also an object-oriented programming language. Are all of those 2GLs? SQL is a partially declarative, domain specific language for database queries from the 80s. And TeX is a domain specific language for typesetting from the 70s. Are they both 4GLs since they are both more or less domain specific?
