In anatomy or biology, a small rounded enlargement or knob-like structure, particularly the expanded tip of a nerve fiber that makes connections with other cells.
From French 'bouton' meaning 'button,' derived from Frankish 'buton,' which literally refers to a small rounded protrusion (like a button on clothing).
Your brain cells communicate through structures literally called 'buttons'—synaptic boutons are the tiny bulbs at the ends of nerve fibers that release neurotransmitters, showing how scientists borrowed everyday language to describe microscopic architecture.
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