念入り|ねんいりnen'iri[0]heiban (flat)

1. na-adjective, nouncareful; scrupulous; thorough; conscientious; elaborate; deliberate; attentive
   ジョンは、念入ねんいりにその事故じこを調査ちょうさした。↗

   John investigated the accident thoroughly.

• Synonym丹念たんねんWrittenWritten/formal prose. Suggests doing something painstakingly, with devoted care — typical of handwork and investigations. Very close in sense to 「念入り」.
• Synonym入念にゅうねんWrittenWritten/formal prose. Careful and thorough, as in 「入念な準備」; 「念入り」 is the more conversational of the two.
• Synonym綿密めんみつWrittenWritten/formal prose. Describes plans or investigations that are tight and leave nothing out; 「念入り」 stresses doing the work itself conscientiously.
• Synonym周到しゅうとうWrittenWritten/formal prose. Covers thorough preparation and forethought, often as 「用意周到」; 「念入り」 stresses care in the way an action is carried out.
• Synonym注意深いちゅういぶかいNeutralNeutral. About staying alert and watchful at every step; 「念入り」 is about taking time and effort to do a job carefully.
• Synonym細心さいしんWrittenWritten/formal prose. Careful attention to detail, usually in the set phrase 「細心の注意」; 「念入り」 stresses doing the work conscientiously.
• Related詳しいくわしいNeutralNeutral. Says content is detailed or that someone knows a subject inside out; 「念入り」 describes how a task is done.
• Related慎重しんちょうNeutralNeutral. Prudence — acting with care so as not to slip up; 「念入り」 stresses doing the job thoroughly and carefully.
• Related詳細しょうさいNeutralNeutral. Refers to detailed content or particulars; 「念入り」 describes the manner of doing something.
• Related細密さいみつWrittenWritten/formal prose. Extremely fine detail, said mainly of paintings and crafts; 「念入り」 describes an attitude toward the work.
• Related丁寧ていねいNeutralNeutral. The most common choice: it covers both politeness and careful, conscientious work; 「念入り」 means only careful, with no nuance of courtesy.
• Related緻密ちみつWrittenWritten/formal prose. Fine-textured structure or a rigorous, leak-proof plan; 「念入り」 stresses how conscientiously something is done.
• Related精細せいさいWrittenWritten/formal prose. Crisp, clearly rendered detail, as in 「高精細」 screens; 「念入り」 describes how a task is done.
• Related精緻せいちWrittenWritten/formal prose. Fine and precise, said mainly of theories and craftsmanship; 「念入り」 is the more everyday word.
• Related徹底的てっていてきNeutralNeutral. Exhaustive, leaving nothing untouched, as in 「徹底的に調べる」; it stresses thoroughness more strongly than 「念入り」.
• Related細かいこまかいNeutralNeutral. Small or fine, also trivial matters or nitpicking; 「念入り」 is a positive word for careful, conscientious work.
• Related事細かことこまかNeutralNeutral. Mostly in 「事細かに説明する」, covering every last detail; 「念入り」 is about doing something conscientiously.
• Related細々しいこまごましいNeutralNeutral. Very fine or minute, also fiddly and complicated with a hint of tedium, and less common; 「念入り」 is a positive word for careful work.
• Antonym粗雑そざつWrittenWritten/formal prose. Coarse and slapdash — the direct opposite of the care that 「念入り」 implies.
• Antonymいい加減いいかげんCasualColloquial. Perfunctory and irresponsible, doing things half-heartedly — the opposite of 「念入り」.

For everyday 'careful', 「丁寧」 and 「念入り」 are the go-to words: 「丁寧」 is the most common but also covers politeness, while 「念入り」 is purely about care. In written prose prefer 「入念」 or 「丹念」. For tight, gap-free plans or investigations use 「綿密」 or 「周到」, and for leaving nothing undone use 「徹底的」. 「慎重」 and 「注意深い」 stress caution rather than effort; 「粗雑」 and 「いい加減」 are the opposites.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 念ねんを入いれること。細こまかい点てんまで注意ちゅういして物事ものごとをすること。