～がたい
Extremely difficult to do or accept
You’ll be able to describe actions that are hard to carry out because they are emotionally, morally, or conceptually difficult.
こんな山奥に素晴らしい温泉があるなんて、信じがたい光景です。
konna yamaoku ni subarashii onsen ga aru nante, shinjigatai koukei desu.
What do you think this sentence means?
To find such a marvelous hot spring deep in the mountains is a sight hard to believe.
Describe an emotionally or psychologically difficult action
Attach がたい to the verb stem of cognitive or emotional verbs (like 信じる) to express that doing the action is virtually impossible or hard to fathom ("hard to...", "difficult to believe").
家族で行った旅行は、忘れがたい思い出だ。
kazoku de itta ryokou wa, wasuregatai omoide da.
The trip I took with my family is an unforgettable memory.
この町が好きで、離れがたい。
kono machi ga suki de, hanaregatai.
I love this town, so it's hard to leave.
Attach がたい to the masu-stem
Attach がたい directly to the verb stem (masu-stem). Common collocations include 信じがたい (unbelievable), 許しがたい (unforgivable), 理解しがたい (hard to understand), and 忘れがたい (unforgettable).
何度も約束を破るなんて、許しがたい。
nando mo yakusoku o yaburu nante, yurushigatai.
Breaking promises again and again is hard to forgive.
～にくい vs ～がたい
～にくい says something is hard to do for a practical reason, like a badly written explanation. ～がたい is for things you can hardly bring yourself to do or accept, like believing or forgiving, and sounds more formal.
～にくい, hard to (practically)
彼の説明は理解しにくい。
kare no setsumei wa rikai shinikui.
His explanation is hard to understand.
It is badly explained: a practical difficulty; がたい would sound odd.
～がたい, hard to (accept)
彼の行動は理解しがたい。
kare no koudou wa rikai shigatai.
His behavior is hard to understand.
You can’t accept or make sense of it.
十年一緒に働いた仲間との別れは、言葉では表しがたいほどつらい。
juunen issho ni hataraita nakama to no wakare wa, kotoba de wa arawashigatai hodo tsurai.
Parting with colleagues I have worked with for ten years is painful beyond words.
会社の突然の決定は、社員にとって受け入れがたいものだった。
kaisha no totsuzen no kettei wa, shain ni totte ukeiregatai mono datta.
The company’s sudden decision was hard for the employees to accept.
どちらの案にもよいところがあって、どちらも捨てがたい。
dochira no an ni mo yoi tokoro ga atte, dochira mo sutegatai.
Both plans have good points, so it’s hard to give up either one.
7 more examples in the grammar path — free for a limited time.