Meaning of $\triangleright$ in programming language semantics What does the symbol "$\triangleright$" mean programming language semantics?  I've seen it in the context of datatypes in and the evaluation of expressions in environments.

For example :

$$tenv \triangleright erht \implies tval $$

or

$$tenv[tval/x]\triangleright ebody\implies t\,.$$

Here, $tenv$ is an environment and $ebody$ is the body of some expression.
Most probably, in your context, ▹ is just a syntactic separator, meaning "in the environment to the left of ▹, the formula to the right of ▹ holds".

However, ▹ has no fixed meaning in general. I used it myself with completely different definitions.