深長|しんちょうshinchou[0]heiban (flat)

1. na-adjective, nounprofound

• Synonym深遠しんえんWrittenWritten register. Points to thought or principles that are deep and unfathomable, as in 「深遠な哲学」; unlike 「深長」, it does not stress what is implied beyond the words.
• Synonym深奥しんおうWrittenWritten but rare. Points to the hidden depths or mysteries of an art or field of learning rather than to suggestive wording.
• Related奥深いおくふかいNeutralNeutral. Says content is deep and thought-provoking, and can also describe how far back a cave goes; more everyday than 「深長」.
• Related深いふかいNeutralNeutral and the most common everyday choice. Covers physical depth, degree, and more, with by far the widest range of use.
• Related奥妙おうみょうWrittenWritten but rare. Points to something unfathomably deep and secret, a hidden mystery, rather than to suggestive meaning.
• Antonym浅短WrittenWritten but rare antonym. Means shallow and short-sighted, the direct opposite of 「深長」 with its far-reaching, suggestive meaning.

Use 「深長」 for words or remarks whose meaning is far-reaching and thought-provoking — in practice almost only in 「意味深長」. For deep, unfathomable thought say 「深遠」; for content with real depth say 「奥深い」; 「深い」 is the everyday all-purpose word.

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

1. 意味いみなどが奥深おくふかく含ふくみのあるさま。