Grown – To undergo natural development to maturity.
God used this word 23 times in Scripture: 22 time to Israel in the Masoretic Text Old Testament; and once to Israel in the Koine Greek Old Testament. 10 times referring to being a fully developed human, 5 times referring to a person’s hair, 5 times referring to plants, and 3 times referring to status.
God never used the words adult or mature. The word grown states that the natural progression of growth results in full maturity. And, according to God, there is no specific age that results in full maturity. But God did use specific words that refer to different stages of maturity.