The Hebrew word is raqia, which is translated "firmament" all 17 times in the King James Version of the Bible, according to Young's Analytical Concordance. Firmament is also used in the NKJV and RSV. The New English Bible and Jerusalem Bible use vault, suggesting a hollowness. The New International Version uses expanse, and the New Living Translation uses space, similar in meaning to our usage for what is beyond our atmosphere.
Next we can look at the properties of the firmament. On the fourth day (Genesis 1:14-19), God places lights in the firmament: the sun, the moon, and the stars (and related objects). So, the firmament includes the universe above the earth's atmosphere.
On the fifth day God said (Genesis 1:20b) ". . . 'and let birds fly above the earth across the face of the firmament of the heavens.' " That means that the firmament is the backdrop when the birds fly above us, though a small number of translations and paraphrases indicate that the birds are within the firmament. So, the firmament may include the near parts of the atmosphere.
The English word firmament suggests something firm or solid, and there is a single verse, Job 37: 18, which seems to mention that property. Referring to Himself, God asks Job, " 'With Him, have you spread out the skies, strong as a cast metal mirror?' " But in this case, the skies comes from the Hebrew shachaq, meaning small dust, a thin cloud, according to Young's. So, I find it unwise to stress such a hard, solid property of the firmament based on a single isolated verse.
The Hebrew word for "waters" is the plural mayim, meaning "water," which is used 570 times in the Bible, with only two other water-related meanings.
For divide, the Hebrew is badal, and Young's gives several English word usages with very similar meanings including separate (26 times), divide (9 times), sever (3 times), and difference (4 times).
Hebrew for "made" is asah, translated "to do" (1292 times), "make" (631 times), "work" (71 times), as well as numerous minor variations all concepts we would expect from a Creator who made everything.
For "heaven" or "heavens," the Hebrew is the plural shamayim, used 398 times. There are also 21 translations as "air," always with various birds of the air. The Genesis 1:8 declaration that the firmament is heaven then allows the lower firmament to be the atmosphere.
Day 2, Words, Heavens, Stretched, Atmosphere, Magnetic, Ending