Machaira (G3162) refers to a sword — typically a shorter sword or dagger used for close combat, distinct from the rhomphaia (large broadsword). It is the word used for the sword of the Spirit in Ephesians 6 and for the double-edged sword in Hebrews 4.
Hebrews 4:12 declares: 'The word of God is alive and active. Sharper than any double-edged sword (machaira), it penetrates even to dividing soul and spirit.' The Scripture is not merely informative but surgically precise — it cuts between what is false and true in the innermost person. Ephesians 6:17 calls it 'the sword of the Spirit, which is the word of God' — the believer's one offensive weapon in spiritual warfare.