1. Vapor or fumes may condense on piping, ducts, or stack walls. �������������ڹܵ����̵����̴ѱ���������
2. When an aroma is sensed, the molecules from the vapor interact with numerous receptors, causing them to send a signal to the brain. ��ij����ζ���о���ʱ�����������ķ�����Ϊ���ڶ�ĸй�����ã��������ǽ��ź��͵����ԡ�
3. As the planet approached its current size, however, its gravitation became strong enough to hold gases and water vapor around it as an atmosphere. Ȼ���������ǽӽ����ڵĴ�С��ʱ����������ǿ�������Ա�������Χ�������ˮ�������γɴ����㡣
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n.
1. a visible suspension in the air of particles of some substance
2. the process of becoming a vapor