Hypotassō (ὑποτάσσω) is built from the preposition hypo (ὑπό, under) and the verb tassō (τάσσω, to arrange, to draw up in order, originally a military term for taking one's appointed station). The compound carries the field of placing oneself in an ordered relationship. In the active voice it can mean to subject or subordinate. In the middle voice, which Paul uses in Ephesians 5:21 (hypotassomenoi, ὑποτασσόμενοι), the action returns to the subject: the believer voluntarily takes his place under, alongside, in support of. BDAG distinguishes the active and middle ranges sharply. Louw-Nida 36.18 places the middle in the domain of voluntary participation in an ordered relationship.

The grammatical hinge for Ephesians 5 is that 5:21 is a participle governing 5:22. The verb of submission in 5:22 is borrowed from 5:21, where the subject is plural and reciprocal: every believer submitting to every other. The wife's submission in 5:22 is one expression of that mutual submission, not a separate unilateral obligation. The English word obey (Greek hypakouō, ὑπακούω) is conspicuously absent from the wife's command; Paul uses hypakouō in Ephesians 6 for children and slaves, but not for wives. He had the verb available. He chose hypotassō in the middle, governed by mutual submission. The translation tradition that flattens hypotassō to obey collapses the grammatical structure Paul built.

Cynthia Long Westfall's work on the middle voice (Paul and Gender, 2016) and Philip Payne (Man and Woman, One in Christ, 2009) develop the lexicography in detail. The Septuagint uses hypotassō for ordered arrangement in cosmic and military contexts (Psalms 8:7, 1 Chronicles 22:18), reinforcing the place-taking sense rather than the subjugation sense.