function as something/someone
phrasal verb with function verb [ I ] uk/ˈfʌŋk.ʃən/ us/ˈfʌŋk.ʃən/
充当;当作;起…的作用
to perform the purpose of a particular thing or the duties of a particular person
We have a spare bedroom that also functions as a study. 我们有一间空卧室可以当书房用。