ざるを得(え)ないCan't help doing, Have no choice but

Both てならない and ざるを得ない convey inevitability, but differ in source. てならない expresses uncontrollable emotion or sensation, as in 会いたくてならない (I can’t help wanting to see them), while ざるを得ない indicates being forced to act due to circumstance or necessity, as in 行かざるを得ない (I have no choice but to go).

ざるを得ない and ないわけにはいかない both express unavoidable action, but differ in tone and motivation. ざるを得ない emphasizes external compulsion or lack of options, as in 行かざるを得ない (I have no choice but to go), while ないわけにはいかない conveys a sense of moral or social obligation, as in 手伝わないわけにはいかない (I can’t not help).

〜ざる is the classical negative form of a verb, functioning like ない when modifying nouns, as in 知られざる名作 (an unknown masterpiece). It also forms the base of ざるを得ない, which conveys inevitability or lack of choice, as in 行かざるを得ない (I have no choice but to go). While 〜ざる alone is literary or archaic, ざるを得ない remains common in formal modern Japanese.

Both express uncontrollable actions or feelings, but differ in tone. ずにはいられない often has a more subjective or emotional feel, e.g. '泣かずにはいられなかった' ('I just couldn't help but cry'). ざるを得ない has a more objective tone and is used to express external necessity or obligation, e.g. '行かざるを得ない' ('I have no choice but to go').

Both express an obligation, but from different perspectives. を余儀なくさせる implies forcing someone into a difficult situation, e.g. 退去を余儀なくさせる 'it (e.g. the situation) forced them to leave' vs. 退去せざるを得ない '(we/I) have no choice but to leave'.

しかない and ざるを得ない both express having no choice, but しかない is more neutral and conversational, e.g. やるしかない ('I have no choice but to do it'). ざるを得ない has a similar meaning but is more literary, and is found mostly in writing or formal speech, as in 行かざるを得なかった ('I was forced to go').

ざるを得ない expresses unavoidable action due to external circumstances, as in 行かざるを得ない (I have no choice but to go). By contrast, てたまらない conveys an intense emotional feeling that is hard to endure, as in 会いたくてたまらない (I can’t help wanting to see you). Both imply compulsion, but one is situational, the other emotional.

ざるを得ない and てしょうがない both express inevitability, but differ in cause and nuance. ざるを得ない conveys compulsion due to external pressure or lack of alternatives, as in 行かざるを得ない (I have no choice but to go), while てしょうがない expresses an overpowering personal emotion or state, as in 寂しくてしょうがない (I can’t help feeling lonely).