expression

legacy system

outdated software or hardware still in use

In more detail

1. (noun) an old computer system or software that is still in use in an organization, even though it is outdated and may be difficult to maintain or update

2. (noun) something, such as a system or way of doing things, that has existed for a long time and is hard to change or improve

Examples

1. The bank still relies on a legacy system from the 1990s to process customer accounts.
2. Moving away from the legacy system requires significant investment and training.

How to use legacy system

Legacy system is used in business and IT contexts to refer to older technology infrastructure that organizations continue to rely on despite its age and limitations. It carries a neutral to slightly negative connotation, suggesting the system is outdated but necessary. The term is more technical and specific than the general synonyms, making it preferred in professional IT discussions.

Common phrases

maintain a legacy system
migrate from legacy systems
legacy system support
replace a legacy system
legacy system modernization
legacy system integration

Synonyms

legacy technology · outdated system · inherited system · old platform · established infrastructure

Opposites

modern system · cutting-edge technology · new platform

Word family

legacy (noun/adjective) · legacies (plural)

A common mistake

Learners sometimes treat 'legacy system' as purely negative when it can be neutral—organizations may maintain legacy systems because they are reliable, contain critical data, or support essential business functions rather than out of negligence.

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