But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil.
Them that are of full age, х teleion (G5046)] - 'perfect:' akin to "perfection" (Hebrews 6:1).
By reason of use, х hexin (G1838)] - 'habit.' Senses - organs of sense.
Exercised - similarly connected with "righteousness" in Hebrews 12:11.
To discern both good and evil - as a child no longer an infant (Isaiah 7:16): able to distinguish between sound and unsound doctrine. The mere child puts into its mouth things hurtful and things nutritious, without discrimination; not so the adult. Paul warns them against being carried about by strange doctrines through not discriminating (Hebrews 13:9).