This wiki page: https://wiki.haskell.org/Referential_transparency talks about "C and ML are languages with constructs that are not referentially transparent." My question is, what is "Constructs"? Is it an abstract concept? Thanks.
"Construct" is being used as a general noun for things that can be constructed in those languages. You could use "thing" instead without really changing the meaning: C and ML contain things that are not referentially transparent.