also: うちまご
grandchild from one's son (especially the heir)
Refers specifically to a grandchild born to one's own son, as opposed to a daughter's child (外孫). Often used in contexts of family lineage and inheritance.
When my eldest son had a child (my grandchild), the house became lively.
There are cases where inheritance treatment differs between grandchildren from a son and those from a daughter.
Standard kanji form; the reading うちまご is the most common.
Alternate on'yomi reading; less common in everyday speech.
Compound of 内 (inside, one's own) and 孫 (grandchild). The reading うちまご is the native Japanese reading, while ないそん is the Sino-Japanese reading.