ろくに〜ない details
not properly + write + not
roku ni kakanai
not properly; hardly at all — criticizes the manner or adequacy of an act, not its degree
meaning: not write properly
このところ忙しくて、ろくに練習していない。
kono tokoro isogashikute, roku ni renshuu shite inai.
I've been busy lately, and I haven't been practicing properly. neutral
あの人、ろくに調べもしないで文句ばっかり言うんだよ。
ano hito, roku ni shirabe mo shinaide monku bakkari iu n da yo.
That guy complains nonstop without even looking into things properly. casual
Examples
not properly; hardly at all — criticizes how inadequately, half-heartedly, or rarely an act was carried out
このところ忙しくて、ろくに練習していない。
kono tokoro isogashikute, roku ni renshuu shite inai.
I've been busy lately, and I haven't been practicing properly. neutral
あの人、ろくに調べもしないで文句ばっかり言うんだよ。
ano hito, roku ni shirabe mo shinaide monku bakkari iu n da yo.
That guy complains nonstop without even looking into things properly. casual
昨夜はろくに眠れなかったので、頭がぼんやりしている。
sakuya wa roku ni nemurenakatta node, atama ga bon'yari shite iru.
I hardly slept a wink last night, so my head feels foggy. neutral
Formation
ろくに{V-nai}attaches to ない-form
Notes
act, not a state. Almost always critical: the speaker is disappointed,
not neutrally reporting a fact.
Related patterns
Similar
Both mark an act falling short, but ろくに〜ない says the act, if it happened at all, was done poorly or insufficiently, while Vもしない says a minimal expected act didn't happen even once — usually set against an explicit contrast (それなのに) rather than criticizing HOW it was done.
Both are pre-verbal adverbs reaching for a distant ない, but 少しも denies DEGREE ("not even a little") and freely modifies verbs, i-adjectives and na-adjectives alike, while ろくに denies the QUALITY of how an act was carried out, and modifies verbs only, implying it was done badly or barely at all.