1, the meaning of the word is different: family reunion in the word "full", meaning all, total ****, more emphasis on the integrity of the family. The word "合" in "合家团圆" focuses more on the gathering and combination of family members.

2, the use of different occasions: family reunion for formal occasions or written expression, more solemn. Family reunion is more commonly used in daily spoken or informal occasions, to express a sense of warmth and cordiality.