Extended Strong's Greek Lexicon (Abbott-Smith based)
futility
Usage: ματαιότης, -ητος, ἡ (μάταιος), [in LXX for הֶבֶל, Psa.31:6 39:5 62:9, al., and nearly 40 times in Ec; for שָׁוְא, Psa.25:4, al.; רִיק, etc. ;] vanity, emptiness, frailty, folly: Rom.8:20, 2Pe.2:18; τ. νοός, Eph.4:17 (elsewhere only in Pollux, 6, 134, and Eccl.).† (AS)