@acer @Alejandro Jakubi

as I type(using the greek letter palette)

`#mi(Δϵ)`(T,Z)

It does display as 

Δϵ(T, z)

Thanks!

@Carl Love 

This works well for me.

By first doing (with an extra space at the beginning of the name)

Δε:=` Δε`:

then the input Δε(T,z) would stay the same for output

@Axel Vogt 

Thanks Axel, 

Delta[epsilon] is a good alternative for the problem, except that ε becomes a subscript of Δ.

For the case in the question, maple may regard Δε(T,z) as a function call rather than an expression. I wonder if there are any way to tell maple to just literally treat Δε(T,z) ? 

@nm @acer 

Perhaps I didn't say clearly.

What I actually want is a formula like this 'Δε（T,z）', when I post the code from maple here, it becomes `Δε`(T, z)... Anyway, I was deducing some physical formulas using maple, AND I want to make it easy to read, like a document. So it will be very helpful to stay with the physics conventional symbols like  'Δε（T,z）'.

However,

My problem is, everytime I type  'Δε（T,z）' in maple, it becomes 'T Δε z'