can you tell me the definitions and relationship of these: depreciation, accumulated depreciation, book value,

Answer 1

Depreciation - the reduction to the cost of an asset. It is an expense

Accumulated Depreciation - depreciation taken on an asset to date. It is a contra-asset. Assets normally have a debit balance on a balance sheet. a contra asset has a credit balance.

Book Value - the cost of an asset less accumulated depreciation.

Example:
Automobile Cost $15,000
Accumulated Depreciation: ($10,000)
Book Value: $ 5,000

Answer 2

Depreciation: The reduction in value of an asset over time, due to age, wear, etc.

Accumulated Depreciation: The depreciation taken to date.

Book Value: Cost minus accumulated depreciation.