Englishfor English speakers
membrane
Noun
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A membrane is a thin layer of cells or tissue that acts as a boundary or lining that separates two environments.
whistle
Noun
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A whistle is a sound like music. A person makes a whistling sound by blowing air when the person's mouth is in a little circle.
The whistle of the wind in trees was low and sad.
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A whistle is a little instrument made of wood, metal or other material. A person puts the instrument in the person's mouth and blows air to make a loud whistling sound.
When you are in danger, blow your whistle loudly and someone will run and help you.
whistle
Verb
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To whistle is to make a whistling sound with one's mouth.
A happy person is able to whistle and work at the same time.