in practice

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Actually, in fact, especially as opposed to theoretically or in principle For example, In practice this contraption seems to work, although no one knows how or why. [ Second half of 1500s ]
Also see: put into practice
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In the exercise of a particular profession, as in She's an obstetrician and has been in practice for at least ten years. [ c. 1700 ]
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In a state of being exercised so as to maintain one's skill, as in This trumpeter is always in practice. [ Early 1600s ]
For an antonym, see out of practice