Dictionary entry and derived forms, were they equal at some point?


I will first state the dictionary entry, and then other formations that also
yield the dictionary entry.

Consider the following :

  1. 思える - to seem/appear, 

    * potential form of 思う - can think
  2. 合わせる - to join together, 

    * potential form of 合わす - can join together

    * causative form of 合う - to let suit/match/agree with

  3. 解ける - to come untied / be solved

    * potential form of 解く - can untie/solve
  4. 空ける - to empty

    * potential form of 空く - can become empty

As above, there are words that in their potential/causative form that already
have a dictionary meaning that is different from their conjugated forms.

**(Question)** Were they equal in meaning at some point in time? Or are they
completely different words and should be treated as such?




Not all of what you claim as potential form are potential forms. Actually, all
`-e-` except for the one in `思える` just switch transitivity.

You seem to be doing the conjugation wrong. Notice that when the verb stem
ends with a vowel, the potential affix is `-re-` instead of `-e`, which is
only for when the verb stem ends with a consonant.

> omow-u → omou (tr.) 'think'  
>  omow- **e** -ru → omoeru (tr. potential) 'can think'
>
> aw-u → au (it.) 'meet'  
>  aw- **e** -ru → aeru (it. potential) 'can meet'
>
> aw-ase-ru (tr.) 'meet'  
>  aw-ase- **re** -ru (tr. potential) 'can meet'
>
> tok-u (tr.) 'solve'  
>  tok- **e** -ru (tr. potential) 'can solve'
>
> tok-e-ru (it.) 'dissolve'  
>  tok-e- **re** -ru (it. potential) 'can dissolve'
>
> ak-u (it.) 'open'  
>  × ak- **e** -ru (it.) 'can open'
>
> ak-e-ru (tr.) 'open'  
>  ak-e- **re** -ru (tr. potential) 'can open'

