age; it is a unit of geological time which is distinguished by some feature like an ice age

ABSCISSION ZONE

THE ABSICISSION ZONE IS THE AREA AT THE LEAF BASE OF LEAF'S PETIOLE ,A  FRUIT STALK ,OR A BRANCH IN WHICH THE SEPERATION (absicission) LAYER DEVELOPS.....

achene

it is a dry, indehiscent one-seeded fruit with a leathery pericarp that is easily separated from seed coat
example; sun flower

ABAXIAL

ABAXIAL

IT MEANS BEING LOCATED ON THE SIDE AWAY FROM THE AXIS .THE ABAXIAL SURFACE OF A LEAF IS ITS UNDERSIDE