副詞 hitherto:

1. used in negative statement to describe a situation that has existed up to this point or up to the present time
   同義詞：so far, thus far, up to now, heretofore, as yet, yet, til now, until now

1. In the execution of a computer program, to load a segment of the computer program in a storage area hitherto occupied by parts of the computer program that are not currently needed.
   在計(jì)算機(jī)程序執(zhí)行中，把一個(gè)計(jì)算機(jī)程序段裝入在此以前被當(dāng)前不需要的程序部分所占用的存儲(chǔ)器區(qū)域中。參閱formoverlay。
2. This is a fact hitherto unknown.
   這是一個(gè)至今無人知道的事實(shí)。

hith.er.to

adv.（副詞）
Until this time:
迄今：到目前為止：
例句：
The weather, which had hitherto been sunny and mild, suddenly turned cold.
迄今一直晴朗溫暖的天氣突然變冷了