【JLPT N4 Grammar】～てはいけない／てはだめだ／てはならない
Conjugations
Verb -Te form＋はいけない(wa ikenai)／ちゃいけない(cha ikenai)／じゃいけない(ja ikenai)
Verb -Te form＋はだめだ(wa dameda)／ちゃだめだ(cha dameda)／じゃだめだ(ja dameda)
Verb -Te form＋はならない(wa naranai)／ちゃならない(cha naranai)／じゃならない(ja naranai)
Meaning
may not, must not, cannot, should not
Explanation
It is a sentence pattern indicating prohibition.
“～てはいけない” and “～てはならない” both indicate prohibition, but the usage range is slightly different.
”～てはいけない” is used when teachers, mothers, bosses, etc. those having higher status tell something to those having lower status. The feature is that the behavior is banned by the command tone.
ㆍ In general, "～てはならない" is often used as a caution or commandment under special circumstances.
In spoken language, people use ”～ちゃ/じゃ" forms, such as "~ちゃいけない" "～じゃいけない"
Examples
（１） 授業中は携帯電話を使ってはいけない。
jyugyo chuu wa keitaidenwa wo tsukatte wa ikenai
You may not use cell phones during class.
授業 jyugyo -class
中 chuu -during, inside
は wa - topic particle
携帯電話 keitai denwa - cell phone
をwo -direct object particle
使う tsukau - to use (te form= 使って)
はいけない wa ikenai- may not
（２） そんな態度をしてはだめです。
Sonna taido wo shite wa dame desu
You must not show that attitude.
そんな sonnna- such, like that
態度 taido- attitude
を wo- direct object particle
