2021-04-30 12:02:51 UTC
The following is an excerpt from <https://www.quword.com/etym/s/a>:
a: [OE] The indefinite article in English is ultimately identical with the word one (as is the case, even more obviously, in other European languages – French un, German ein, and so on). The ancestor of both a(n) and one was ān, with a long vowel, but in the Old English period it was chiefly used for the numeral; where we would use a(n), the Anglo-Saxons tended not to use an article at all. Ān begins to emerge as the indefinite article in the middle of the 12th century, and it was not long before, in that relatively unemphatic linguistic environment, its vowel became weakened and shortened, giving an.
In the first sentence mentioned above, there is a clause induced by as, i.e., "as is the case". But to be frank, this short little word seems so difficult for me to master all its usage scenarios. Any hints/notes/explanations for the above case will be highly appreciated.