The activity of conveying information and ideas to others through the exchange of speech, written messages, signals or behaviour such as body language.
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Deltiology是指收集和研究明信片，通常是作为一种业余爱好。
卫星在一个环绕地球的轨道行驶传接从地球一个地方发出的信号并且将信号再发送到地球的另一个地方。
