The Hebrew word translated 'heaven' is shamayim. This word exists only in the plural form, not meaning that there is more than one heaven, but indicating the largeness and vastness of heaven. The same word can also be translated 'sky' depending on the context. The Greek word translated 'heaven' is ouranos. This word is used in the New Testament in exactly the same way shamayim is used in the Old. It can refer to the sky where the birds fly (Revelation 19:17); it can refer to outer space where the stars shine (Isaiah 13:10); and it can refer to the habitation of God (1 Kings 8:30). The first heaven can only be seen by day, the second only by night, and the third only by faith!