I recently corrected someone's use of beit hamidrash to beit-midrash, explaining that it is a smichut pair like the similar pairs, beit-knesset and beit-sefer, and that the added hei is only appropriate if it refers to a specific beit-midrash and is therefore a proper noun.
I then compared it to the use in Genesis 1 and 2 of yom hashishi and yom hash'vii, contrasting them with the same word pairs but without the hei. I suggested that without the hei, they refer to days of the week, but in Genesis 1 and 2 they are days 6 & 7 of a specific week - the week of creation - and are therefore like a proper noun, hence the hei. The trouble with that explanation is that, if so, why is there no hei for the earlier days (at least days 2 to 5)? Ibn Ezra on Gen 1:31 gives two examples of word-pairs in smichut with a hei prefixed to the second word, but I think both examples could be proper nouns. So I ask:
- Am I right in saying that a hei should only be prefixed to the second word of a smichut pair if it is a proper noun? and
- Why the difference in Genesis 1 between yom-sheini and yom hashishi? (I note the midrashic explanation cited by Rashi, but I am wondering if there is a grammatical explanation.)