Hypostasis

Hypostasis is a Greek word ὑπόστασις that has a range of meanings:  nature, substance, image, essence, etc.  It is translated as "nature" in the NASB in Heb. 1:3, "And He is the radiance of His glory and the exact representation of His nature, and upholds all things by the word of His power." It is translated as "image" in the ASV, KJV and NKJV, "imprint" in the ESV and NRSV.  It is also found in

• 2 Cor. 9:4,"otherwise if any Macedonians come with me and find you unprepared, we—not to speak of you—will be put to shame by this confidence [hypostasis]," (NASB).
• Heb. 3:14, "For we have become partakers of Christ, if we hold fast the beginning of our assurance [hypostasis] firm until the end," (NASB).
• Heb. 11:1, " Now faith is the assurance [hypostasis] of things hoped for, the conviction of things not seen," (NASB).

It is borrowed for the English term Hypostatic Union which is the teaching that in the one person of Christ, are two natures.