αναποτελεσματικός

From LSJ

καὶ τὸ σιγᾶν πολλάκις ἐστὶ σοφώτατον ἀνθρώπῳ νοῆσαι → and silence is often the wisest thing for a man to heed, and often is man's best wisdom to be silent, and often keeping silent is the wisest thing for a man to heed

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