The glass is twice as big as it should be.

(Programming joke)

i say both Um

It depends within a literal lense. If I poured it halfway, it's half full. If It was already full & I drank it halfway, it's half-empty. Figuratively, my answer is "there's water in the cup & it should be filled further."

depends on how it got there. if the glass was filled halfway, then its half full. if it had more but was emptied to be half empty, then its half empty. if there's no context then id just say whatever comes to mind

Half full :)

half empty! ☝🏻

half full

it depends on the context and I refuse to give an answer that works in a normal context

it's 100% full, half air and half water

or it's significantly more than half full, some of it is filled with glass

or it's mostly empty, if you consider water to be "empty" as I assume a fish would