Hard, Harden, Hardening, Hardness - Vine's Expository Dictionary of New Testament Words
Hard, Harden, Hardening, Hardness[ A-1,Adjective,G4642, skleros ]
from skello, to dry," signifies "trying, exacting:" See AUSTERE.
[ A-2,Adjective,G1422, duskolos ]
primarily means "hard to satisfy with food" (dus, a prefix like Eng., un, or mis, indicating "difficulty, opposition, injuriousness," ect., the opposite of, eu, "well," and kolon, "food"); hence, "difficult," Mark 10:24, of the "difficulty," for those who trust in riches, to enter into the Kingdom of God.
[ B-1,Noun,G4643, skelerotes ]
akin to A, No. 1, is rendered "hardness" in Romans 2:5.
[ B-2,Noun,G4457, porosis ]
denotes "a hardening," a covering with a poros, a kind of stone, indicating "a process" (from poroo, C, No. 1), and is used metaphorically of dulled spiritual perception, Mark 3:5, RV, "at the hardening of their hearts;" Romans 11:25, RV, "a hardening" (AV, "blindness"), said of the state of Israel; Ephesians 4:18, RV, "hardening," of the heart of Gentiles. See BLINDNESS.
Note: See also under HARDSHIP and HEART (hardness of).
[ C-1,Verb,G4456, poroo ]
"to make hard, callous, to petrify" (akin to B, No. 2), is used metaphorically, of the heart, Mark 6:52; Mark 8:17; John 12:40; of the mind (or thoughts), 2 Corinthians 3:14, of those in Israel who refused the revealed will and ways of God in the Gospel, as also in Romans 11:7, RV, "hardened" (AV, "blinded"), in both places. See BLINDNESS.
[ C-2,Verb,G4645, skleruno ]
"to make dry or hard" (akin to A, No. 1 and B, No. 1), is used in Acts 19:9; in Romans 9:18, illustrated by the case of Pharaoh, who first persistently "hardened" his heart (See the RV marg. of Exodus 7:13, Exodus 7:22; Exodus 8:19; text of Exodus 8:32; Exodus 9:7), all producing the retributive "hardening" by God, after His much long-suffering, Exodus 9:12, etc., in Hebrews 3:8, Hebrews 3:13, Hebrews 3:15; Hebrews 4:7, warnings against the "hardening" of the heart.