にくい

1. 1An action is difficult to carry out, usually because of some property of the thing or situation involved.Ex. 1
2. 2Something does not happen easily, describing an object's tendency to resist a change (e.g. 割れにくい, 'hard to break').

Neutral in register and common in both speech and writing, for describing everyday difficulties with objects, tools, places, or tasks, as well as physical properties like durability. It is the direct opposite of やすい, 'easy to do'. Compared with づらい, にくい tends to present the difficulty as objective rather than as the speaker's personal discomfort.

• づらいN4「づらい」attaches the same way, but emphasizes the actor's subjective discomfort from physical inconvenience or psychological burden, as in「言いづらい」. It is used for volitional human actions and is not suitable for describing properties of objects, such as being hard to break.
• がたいN3「がたい」attaches the same way, has a formal tone, is mostly seen in writing, and emphasizes that something is almost impossible to realize. It often pairs with「信じる」「許す」and can also describe objective difficulty, as in「扱いがたい」. For everyday talk about whether an object is easy to use,「にくい」is the right choice.
• やすいN4「やすい」is the opposite in meaning: it indicates an action is easy to do, a change is likely to occur, or something has a certain tendency; it can also describe a person's constitution or personality (e.g.,「風邪をひきやすい」). Its attachment, conjugation, and register are the same as「にくい」, but the two cannot be swapped.
• かねるN2「かねる」is not about objective difficulty; it expresses that something is inconvenient to do due to one's position, rules, or propriety (often as a polite refusal), or psychological hesitation or being unable to bear it (e.g.,「決めかねる」). It has a formal tone and generally cannot be interchanged with「にくい」.
• ようがない / ようもないN2「ようがない」means there is simply no way to do something — it cannot be done — whereas「にくい」only means it is difficult but still possible, so the two cannot be interchanged. Both attach to the masu-stem (ます-stem minus ます).「ようがない」also has the form「言いようのない」, which expresses an extreme degree.

づらい stresses the doer's physical or psychological discomfort, while やすい is the opposite, 'easy to do'. がたい is more formal and suggests something is nearly impossible, typically with verbs of thought or emotion (信じがたい); かねる expresses that the speaker cannot do something because of circumstances, often as a polite refusal; ようがない / ようもない mean there is no way or means to do it at all.