To keep someone interested, amused, or engaged. It can also mean to consider an idea or possibility in your mind.
From Old French *entretenir* ('to hold together, maintain, amuse'), from *entre* ('between') + *tenir* ('to hold'), from Latin *tenere* ('to hold'). It moved from 'maintain, support' to 'amuse, occupy attention.'
To 'entertain' is literally to 'hold between'—to keep someone’s attention suspended with you. Even 'entertaining an idea' is like giving it a little mental stage time before you accept or reject it.
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