From the Ministry of John Piper

What kind of humanity did Christ take on? Was it a humanity that was already personal? Or did he somehow take on a kind of impersonal humanity?
The famous all-church Council of Chalcedon in 451 confirmed with clarity that Jesus is “one person” with “two natures” (full divinity and full humanity), but after the council, years of further discussion ensued. How is it that one person can have two natures? When the Son of God took on humanity, did that not mean that he was taking to his divine person a second (human) person as part of that humanity? Is he not two persons, if he as two natures?Enter the theological term anhypostasis. The Greek word hypostasis had come to refer in the early church discussions to what we’d call personhood—whether in the Trinity or in the two-natured person of Jesus—and so the negating an- prefix was added to signify that, considered on its own (apart from his divinity), Jesus’ humanity is impersonal.In other words, Jesus took a fully human nature, but he did not take a human person. Jesus can have a fully human nature without also taking a pre-existing human personhood. Not that his human nature ever existed on its own. It’s a question about a hypothetical reality, intended to give insight into the actual reality.

Heinrich Heppe also captures it nicely: “The humanity taken up into the person of the Logos is, then, not a personal man but human nature without personal subsistence” (Reformed Dogmatics, 416) (归正教义，416).

"Reformed Dogmatics" has been the fountainhead of Reformed theology for the last hundred years. It is by far the most profound and comprehensive Reformed systematic theology of the twentieth century.
“改革宗教义“ 一直是过去一百年来改革宗神学的源泉，这是二十世纪迄今为止最深刻，最全面的改革宗系统神学。

基督取了什么样的人性?
基督取了什么样的人性? 是一个已具人格的人性吗？ 还是他以某种方式取了一种非个人 (不具人格的) (Impersonal)的人性？ 著名的全教会迦克墩大公会在451清楚确认耶稣是“一个位格”“两种本性”（完全的神性和完全的人性）, 但是, 会后多年的进一步讨论接踵而至。一个位格 (person) 怎么可以有两个本性？ 当神的儿子取了人性，这不意味着他在给他的神性位格取作为人的一部分的第二个位格？ 如果他有两个本性, 他不是两个位格吗？输入神学术语 anhypostasis。 在早期教会讨论中, 希腊词 "位格"已变成我们所说的人格 (personhood), 无论是在三位一体还是在有两个本性的耶稣的位格讨论中 , 所以, 分开他的神性考虑, 一个否定前缀加入以表示耶稣的人性是非个人的(Impersonal)。
换句话说，耶稣取了完全的人性，但他并没有取一个有位格的人 (human person)。耶稣可以拥有完全的人性，而不取预先存在的人格 (personhood)。这并不是说他的人性曾经独自存在。这是旨在对一个假设性的现实的问题给予真实的现实的见解.

Anhypostasis is a “negative” doctrine, so to speak. It says where Jesus’ singular personhood does not come from.
Anhypostasis是一个否定学说，可以这么说。它说耶稣非凡独特的人格不来自哪里。