1. ~がたい (Hard to / Almost impossible to...)
Meaning: Psychologically or emotionally, it is extremely difficult or almost impossible to do something.
✓ It is not used for physical ability or practical capability.
✓ It commonly follows verbs related to speech or expression, such as 言う and 表す, or verbs of thought and emotion such as 想像する, 理解する, and 信じる.
2. ~わけにはいかない (Cannot / Must not...)
Meaning: For moral, social, or common-sense reasons, one cannot bring oneself to do something.
✓ It is not used for inability based on physical skill or capability.
✓ The subject is often the first person.
3. ~かねる (Unable to / Cannot readily...)
Meaning: Given the speaker’s circumstances, position, or conditions, it is difficult or impossible to do something.
✓ It is not used for mechanical or physical inability.
✓ Common in formal and business contexts as a polite, indirect way to refuse something.
4. ~ようがない (There is no way to... / Impossible to...)
Meaning: Even if one wants to do something, there is absolutely no method or means available to do it.
✓ Used when there is no possible method or way to carry out the action.
✓ Strongly emphasizes that it is absolutely impossible.
5. ~どころではない (It is no time for... / Not in a position to...)
Meaning: The current situation is so unfavorable that one has neither the time nor the mental room to do the expected or desired action.
✓ Used when circumstances such as lack of money, being extremely busy, noise, illness, etc. make the desired action impossible at the moment.
6. ~得る / ~得ない (Can possibly / Cannot possibly...)
Meaning: Objectively indicates that something is possible or impossible, feasible or infeasible.
✓ The affirmative 得る can be read える or うる; in this grammar pattern it is often read うる. The negative 得ない is always read えない.
✓ It is not used for a person’s individual ability or for situational permission/ability.