G4731–στερεός–stereos

However God's firm foundation stands, having this seal, "The Lord knows those who are his," and, "Let every one who names the name of the Lord depart from unrighteousness."

στερεὸς stereos “the firm”

For when by reason of the time you ought to be teachers, you again need to have someone teach you the rudiments of the first principles of the oracles of God. You have come to need milk, and not solid food.

στερεᾶς stereas “of solid”

But solid food is for those who are full grown, who by reason of use have their senses exercised to discern good and evil.

στερεὰ sterea “solid”

Withstand him steadfast in your faith, knowing that your brothers who are in the world are undergoing the same sufferings.

στερεοὶ stereoi “firm”