以来 means "since", "ever since": from a point in the past up to now, something has stayed the same. It follows a noun, usually an event or a time, or a verb's て-form.
、。
I haven't seen her since graduation.
、。
Ever since I came to Japan, I've been using Japanese every day.
、。
I haven't spoken to him even once since that day.
The verb takes the て-form, not the た-form.
The second half is a state that has lasted up to now, so it is きごう〜, きごう〜, or "never since" with きごう〜.
、。
I haven't taken a single day off since joining the company.
以来 or てから
is "after": one thing, then another. 以来 says a state has held from then until now, so a single event after the starting point takes てから.
。
After moving, I went shopping.
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Ever since I moved, I've been shopping online.
- × 引っ越して以来、買い物に行った → 引っ越してから、買い物に行った
以来 is the more formal of the two. In conversation, often does its job.
Usage notes
These go beyond 以来 after a noun or a verb.
それ以来
, "since then", starts a sentence and points back to the event just mentioned.
、。、。
I had an accident last year. I haven't driven since then.
A starting point worth marking
The starting point is a past event that matters – a graduation, a marriage, an accident, a founding. A moment ago doesn't take 以来: ×さっき以来.
、。
Ever since they got married, the two have been on good terms.
、。
This company has continued to grow since its founding.
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