This is a species where the name gives you the key to identification which is not always the case in nature. The green-ribbed sedge (Carex binervis) has dark green leaves whereas many sedges are pale green or glaucous grey and it has ribbed leaves where many sedges are smooth.
Sedges are interesting as they tend to have a single male 'flower' at the top of the stem and then female flowers below coming alternately from the stem.The shape, arrangement and combination of these two sorts of flower also help to identify it although, even so, sedges can be tricky chaps in my view! In green-ribbed sedge the male flower is tall and slender, the female ones more compact and yet quite large. Both sexes are a purple-brown and they look 'over' even when newly produced.
Green-ribbed sedge can be found on acid soils and, unusually for sedges, they prefer dry ground and so can be found on dry heath and acid grassland where other sedges are less likely to be found.