られる/える

The potential form is used to indicate that an action is possible, that one has the ability to do it, or that one is available to do it. While standard polite requests for favors usually use the potential form of receiving verbs, such as 〜てもらえる, the potential form of an action verb is sometimes used in casual speech as an indirect request (e.g., 「塩、取れる？」 'Can you pass the salt?'). It is also perfectly fine for asking about possibility (like 'Can you come to the party?').

1. Conjugation Rules:
Potential forms always conjugate as 一段（いちだん） verbs once they are formed.

• 五段（ごだん） (Group 1): Change the final う-row kana to the corresponding え-row kana, and add る.
  Example: 行く（いく）→ 行ける（いける）; 待つ（まつ）→ 待てる（まてる）.
• 一段（いちだん） (Group 2): Remove the final る and add られる.
  Example: 食べる（たべる）→ 食べられる（たべられる）. Note: This is identical to the passive form.
• Irregular (Group 3): する becomes できる and 来る（くる） becomes 来られる（こられる）.

2. Particle Changes:
When a transitive verb is changed into the potential form, the object marker を often changes to the subject marker が. Traditionally, が is preferred in formal writing, but in modern Japanese, を is widely accepted and common when the speaker wants to emphasize the action itself. However, when using the irregular verb できる (the potential form of する) with a noun, you must use the subject marker が (e.g., テニスができる, 勉強ができる). Using を directly with a noun plus できる (e.g., テニスをできる, 勉強をできる) is incorrect. If you want to use を in this way, you must use the alternative form 〜をすることができる (e.g., 勉強をすることができる). Note that when the noun and できる form a single compound verb (like 勉強できる), you CAN use を for the target object of that verb (e.g., 日本語を勉強できる is correct).

3. Potential vs. Spontaneous Perception:
There is a critical distinction between the potential form and spontaneous perception verbs:

• Potential: 見られる（みられる） means 'can see' (have the opportunity/permission) and 聞ける（きける） means 'can listen' (have the ability/opportunity).
• Spontaneous: 見える（みえる） and 聞こえる（きこえる） are used when something enters your sight or hearing naturally without effort.

4. Volition Rule & Exceptions:
The potential form generally only applies to volitional verbs (actions a subject can control). It cannot be used with non-volitional intransitive verbs that happen naturally (for example, 雨が降れる（あめがふれる） is incorrect). Additionally, verbs that already describe a state or ability, such as わかる (to understand) or ある (to exist), do not have potential forms. Crucially, once a verb is changed into the potential form, it becomes a non-volitional state verb itself. This means potential verbs cannot be used in the imperative form (e.g., 食べられろ is incorrect) or volitional form (e.g., 食べられよう is incorrect). Furthermore, when expressing purpose, you must use ように instead of ために with potential verbs (e.g., 食べられるように). Additionally, potential verbs cannot be combined with the desire suffix 〜たい (e.g., 泳げたい is incorrect). To express a desire to gain an ability, use 〜ようになる with 〜たい (e.g., 泳げるようになりたい).

5. Alternative Form:
You can also express potential by using the dictionary form of a verb followed by ことができる. This is a slightly more formal alternative that means the exact same thing (e.g., 食べる（たべる）ことができる is the same as 食べられる（たべられる）).

6. ら抜き言葉（らぬきことば）:
In casual conversation, many speakers drop the ら from 一段（いちだん） potential forms (e.g., 食べれる（たべれる） instead of 食べられる（たべられる）). While very common, this is considered informal and should be avoided in polite or academic contexts.