Englishfor English speakers
nucleus
Noun
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A nucleus is the center of a cell or atom.
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The center of anything.
bubble
Noun
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A bubble is a volume of air trapped in a liquid and can float in the air.
The girl made a really big soap bubble.
bubble
Verb
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If something bubbles, it makes bubbles or begins to turn into a bubble.
Wait until the water bubbles before turning off the stove.
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If something bubbles, it begins forming or is created.
bubbled inside of him.