"as far as"是英语中多功能的短语介词/连词，核心含义围绕“范围、程度或距离的极限”，具体用法可分为三大类：
用于描述空间上的最远到达点，常后接地点名词，强调“走到/延伸到某个具体位置”。
例句：We walked as far as the railway station before taking a taxi.（我们步行到火车站才打车。）
The forest stretches as far as the mountains in the distance.（森林一直延伸到远处的山脉。）
这是最常用的引申义，用于限定讨论的范围或视角，引导状语从句（从句主语常为“人/事/物”），相当于“in terms of”或“regarding”。
结构：as far as + 从句（sb./sth. + be concerned/...） 例句：As far as I'm concerned, this decision is a big mistake.（就我而言，这个决定是大错特错。）
As far as English learning goes, practice is more important than theory.（至于英语学习，练习比理论更重要。）
The plan is feasible as far as the budget is concerned.（就预算而言，这个计划是可行的。）
"as far as"常与特定表达结合，形成约定俗成的短语，简化语义：
1、 as far as I know：据我所知（= to the best of my knowledge）
As far as I know, the concert has been canceled.（据我所知，演唱会已经取消了。）
2、 as far as possible：尽可能（= as much as possible）
Please arrive as far as possible by 8:00 AM.（请尽量在早上8点前到达。）
3、 as far as the eye can see：极目所及（= as far as one can see）
From the top of the hill, we saw fields as far as the eye can see.（从山顶望去，我们看到一望无际的田野。）
4、 as far as sb. can tell/remember：据某人判断/回忆
As far as I can tell, he's telling the truth.（据我判断，他在说真话。）
两者语义基本一致，但"so far as"更正式，且多用于否定句（表示“不超过……范围”）；
日常口语中更常用"as far as"。
例句：I don't know her so far as to ask for her help.（我和她不熟，不至于找她帮忙。）
"as far as"的核心是“划清范围”——无论是空间距离、讨论的话题，还是个人的认知极限，都可以用它来限定。记住常见搭配（如as far as I know）和引导从句的用法（as far as sb. is concerned），就能灵活运用啦！