Sometimes Spanish uses two words to describe different aspects of something that English describes with one word. We’ve already seen that un vaso is an ordinary glass without a stem, as opposed to una copa, a glass with a stem, especially a wineglass.
Ni siquiera me ofrecieron un vaso de agua. They didn’t even offer me a glass of water.
Sólo tomé una copa de vino. I only had one glass of wine.
There is a Spanish idiom which uses the word vaso: ahogarse en un vaso de aguato get worked up over nothing, to make a mountain out of a molehill (word for word, ‘to drown in a glass of water’).
Ni siquiera me ofrecieron un vaso de agua. They didn’t even offer me a glass of water.
Sólo tomé una copa de vino. I only had one glass of wine.