Extremely small; a more playful or informal way of saying 'tiny' that's often used when talking to children.
From 'tiny' plus the diminutive suffix '-y' or '-ie,' which makes words sound cuter and smaller. It's a form of baby talk that became common enough to use in everyday speech.
'Teeny' is a linguistic cheat code—adding 'ee' sounds to words actually makes them sound smaller to our brains, which is why 'teeny-tiny' feels smaller than just 'tiny.'
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