Most of the words in the Old Testament that are translated for JOY in Hebrew mean gladness, joy, mirth, rejoicing etc...
Nehemiah 8:10 reads, “Then he said unto them, Go your way, eat the fat, and drink the sweet, and send portions unto them for whom nothing is prepared: for this day is holy unto our Lord: neither be ye sorry; for the 'JOY' of the LORD is your strength.”
That word joy there is Strong's Hebrew H2304, Chedvah. It has such a deeper meaning. It is the only time this word is used in the Bible.
It comes from a primitive root (H2302) meaning 'make glad, rejoice and 'Be Joined'
Being 'joined' to the Lord is our strength and it brings us joy, gladness, cheerfulness etc...
It's that inward knowing that we are joined to Him that gives us joy and strength. It also gives us peace and comfort when we are going through hard times. He is in us and we are in Him. Joined, connected and victorious!
When we are hurting it's hard to feel cheerful and glad but being connected to Him assures us that everything's going to be all right. Yes, it's gonna be all right.