• There is no sharp line of demarcation ( or demarcation line ) between the atmosphere and space.
• The two parts are separated by a dividing line .
• There is no sharp line of demarcation ( or demarcation line ) between the atmosphere and space.
• The two parts are separated by a dividing line .
Циммерман М., Веденеева К.. Русско-Английский научно-технический словарь переводчика. Russian-English scientific dictionary for translators. 2012