Englishfor English speakers
particle
Noun
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A particle is a very small, tiny piece.
His eye hurt because a particle of dust had got into it.
activity
Noun
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When a person or animal has activity, it is active or lively.
The sleeping dog did not show much activity.
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When you have a function to do, you have an activity.
The child has many after-school activities.
She participates in women's rights activities.