a chemical element that is a gas with no smell or colour. ............................ forms a large part of the air on earth, and is needed by animals and plants to live.
OXYGEN
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the force that attracts objects towards one another, especially the force that makes things fall to the ground.
GRAVITY
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the measured amount of heat in a place or in the body.
TEMPERATURE
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all the people living in a particular country, area, or place.
population (n) - (un)populated / populous (a) - populate (v)
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looking or being almost, but not exactly, the same.
(dis)similar (a) - (dis)similarity (n)
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full of people.
(over)crowded (with ...) (a) - crowd (n/v)
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alien (n/a)
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(dis)appear (v) - (dis)apearance (n)
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having a flat circular shape
disk-shaped (a)
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flying saucer / UFO (unidentified flying object)
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tiny - huge (a)
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unusual and unexpected, or difficult to understand; not known or familiar.