Strong’s Greek
G3452 — muelos
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
μυελός
muelos — pronounced moo-el-os'
perhaps a primary word; the marrow:--marrow.
1 occurrence in the KJV.
Hebrews 4:12
For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart.