Easy & hard
The difficulty scale for tasks and situations, from easy through hard and tough to impossible.
kantan
polite kantan desueasy, simple
簡単 かんたん 簡単です
Says a task, recipe, explanation or test is easy or simple; kantan ni means 'simply, briefly'.
kono shigoto, kantan da ne
This job is easy, isn't it?
この仕事、簡単だね
kono shigoto wa kantan desu ne
This job is easy, isn't it?
この仕事は簡単ですね
A na-word: before ne or yo it takes da (kantan da ne), and its past is kantan datta, never kantankatta.
Learn alongside: muzukashii, taihen, muri
muzukashii
polite muzukashii desudifficult, hard
難しい むずかしい 難しいです
Says something is hard to do or understand (tasks, questions, languages, decisions); chotto muzukashii is also a soft way to say no.
kono shigoto, muzukashii ne
This job is difficult, isn't it?
この仕事、難しいね
kono shigoto wa muzukashii desu ne
This job is difficult, isn't it?
この仕事は難しいですね
'Sore wa chotto muzukashii desu' usually means a polite no, not just 'difficult'.
taihen
polite taihen desutough, awful, lots of work
大変 たいへん 大変です
Says a situation is tough, a lot of work or a real problem; 'taihen da ne' is the stock sympathy reply to anyone's hard time, and 'taihen!' alone means 'oh no, trouble!'.
kono shigoto, taihen da ne
This job is tough, isn't it?
この仕事、大変だね
kono shigoto wa taihen desu ne
This job is tough, isn't it?
この仕事は大変ですね
In formal speech taihen also means 'very' (taihen moushiwake arimasen).
Learn alongside: kantan, muzukashii, muri
muri
polite muri desuimpossible, no way, too much
無理 むり 無理です
Says something is impossible or too much for you; 'muri!' or 'kyou wa muri' is the everyday casual refusal, and muri shinaide means 'don't overdo it'.
kono shigoto, muri da ne
No way we can do this job.
この仕事、無理だね
kono shigoto wa muri desu ne
No way we can do this job.
この仕事は無理ですね
Blunt to a superior; chotto muzukashii desu refuses more politely. Everyday casual refusal: ashita? gomen, muri.
Learn alongside: kantan, muzukashii, taihen