Your firstborn is your first child — the one born before any others. It works as a noun ('their firstborn', 'she was the firstborn') and as an adjective before a noun ('his firstborn son').

Your firstborn你的firstborn(長子、長女) is your first child就是你第一個出生的孩子 the one born before any others比其他孩子都早出生的那一個 It works as a noun它可以當名詞用 ('their firstborn'像'their firstborn' 'she was the firstborn'或'she was the firstborn') and as an adjective before a noun也可以放在名詞前當形容詞 ('his firstborn son'像'his firstborn son')

Plain English would just say 'eldest child' or 'oldest son', and in ordinary conversation that is what people say. 'Firstborn' is heavier.

Plain English平白的英文 would just say 'eldest child' or 'oldest son'就只會說'eldest child'或'oldest son' and in ordinary conversation而在日常對話裡 that is what people say人們也是這樣講 'Firstborn'firstborn這個字 is heavier比較有分量

It carries a lot of old weight, because for centuries in many places the firstborn son inherited the land, the title, the family name. So the word does not just record an order of birth; it hints at rights and duties.

It carries a lot of old weight它帶著很多古老的份量 because for centuries in many places因為好幾世紀以來在很多地方 the firstborn son inherited the land, the title, the family name長子會繼承土地、頭銜和家族的姓氏 So the word does not just record an order of birth所以這個字不只是記錄出生的順序 it hints at rights and duties它還暗示著權利和責任

You meet it a great deal in the Bible, in stories, in history, and in formal or emotional writing. That gives it a slightly grand, sometimes solemn sound.

You meet it a great deal你會大量碰到這個字 in the Bible, in stories, in history, and in formal or emotional writing在聖經、故事、歷史,以及正式或感性的文章裡 That gives it a slightly grand, sometimes solemn sound這讓它聽起來有點宏偉,有時甚至莊重

A parent might say 'my firstborn' fondly and half-jokingly about a grown-up child, and everyone hears the warmth in it. But you would not normally ask a stranger 'Is this your firstborn?' — 'Is she your oldest?' is what a real person says.

A parent might say 'my firstborn'父母可能會說'my firstborn' fondly and half-jokingly帶著疼愛又有點開玩笑地 about a grown-up child談起一個已經長大的孩子 and everyone hears the warmth in it而大家都聽得出那份溫暖 But you would not normally ask a stranger 'Is this your firstborn?'但你通常不會問陌生人'Is this your firstborn?' 'Is she your oldest?'而'Is she your oldest?' is what a real person says才是真實人們會說的話

Note the spelling: it is normally one word, firstborn, though you will see first-born with a hyphen in older books and it is not wrong.

Note the spelling注意拼法 it is normally one word, firstborn它通常是一個字,firstborn though you will see first-born with a hyphen in older books不過你在比較舊的書裡會看到加連字號的first-born and it is not wrong這樣寫也沒有錯