How can I use synecdoche in a sentence about someone's reflection in the mirror?
She looked through the glass and saw her image/reflection.
A synecdoche is a figure of speech in which a part is made to represent the whole or vice versa. For example, the word "police" can be used to represent only one or a few police officers. Or facial tissue is often referred to as "Kleenex."
In this case, the glass is referring to the mirror as a whole because glass is one part of the mirror.