Adaptations are characteristics that enable organisms to survive in its particular environment, and can be generally grouped into structural, physiological and behavioural adaptations.
Structural
The physical makeup (morphology) of the animal, e.g streamlined shape of dolphins to assist swimming.
Other examples:
Gills
Large leaves to float
Waxy leaves to prevent excessive water
Exoskeletons
Physiological
Typically features that are not visible and are metabolic/body-chemistry related (e.g excretion of concentrated urine to avoid water loss in desert animals or secretion of toxin by plants)
Other examples:
Efficiently operating kidneys
Change in body shape (e.g erection of body spikes/hair)
Excretion of uric acid crystals
Behavioural
Typically features associated with patterns of activity (e.g being nocturnal to avoid hot weather, or courtship rituals to increase chances of reproduction)
Other examples:
Hiding in burrows or tree trunks to avoid predators