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?

1 Answer 1


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'

  • Does that mean some verbs don't have a potential form? Commented Oct 11, 2011 at 3:55
  • But isn't the formation of short-potential form for 五段 verbs their 連用形+[得]{え}る with sound contraction? E.g. 解く > 解き+得る > 解ける. This means that given any 五段 verb, we can form a potential form for it right?
    – Flaw
    Commented Oct 11, 2011 at 4:11
  • @Flaw 解ける is actually ambiguous between intransitivized form and potential form. And, it has the meaning that you expect. 解く 'solve' vs. 解ける 'can solved'.
    – user458
    Commented Oct 11, 2011 at 4:28
  • @Flaw There is no contraction. 'tok + e + ru > tokeru'
    – user458
    Commented Oct 11, 2011 at 4:29
  • 1
    @sawa for reference, I learned my conjugation schemes here: grammar.nihongoresources.com/doku.php?id=conjugation
    – Flaw
    Commented Oct 11, 2011 at 4:53

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