It seems that with some verbs "each other" is optional but not with others. Is there a general sense of when it is optional? Is there a terminology or concept behind this I can google for further discussion?
For instance, when using "meet" we can discard "each other" without changing the meaning. However when using "know" we cannot.
- We met each other.
- (same as above) We met.
- We know each other.
- (not the same as above) We know.
I don't think of these expressions as reflexive (reflexive would be "We know ourselves" and "We met ourselves" (the latter being awkward/not allowed)). But maybe the use of "each other" is a special case of reflexiveness?
I am interested if "one another" would follow the same rules. (I assume it does)