Русско-англо-русский юридический словарь

Accumulated amortization is the cumulative amount of all amortization expense that has so far been charged against an intangible asset. The concept can also be intended to apply to all amortization that has been charged to-date against a group of intangible assets. (accountingtools.com)

Accumulated depreciation is the total depreciation for a fixed asset that has been charged to expense since that asset was acquired and made available for use. The accumulated depreciation account is an asset account with a credit balance (also known as a contra asset account); this means that it appears on the balance sheet as a reduction from the gross amount of fixed assets reported. (accountingtools.com)