Clojure裡面的Higher-Order Function

還是在翻譯《seven programming languages in seven weeks》時遇到了問題。需要請教一下大家。我認為map，filter都是高階函式，但是原書中有兩處讓我感到困惑。

1. We can build a list of the lengths of the names, like this:

user=> (map count people)
(3 8)

You've seen these concepts before. count in this context is a higher-order function.

2. Here are some of the functions on collections that use higher-order functions.

• apply ...
• filter ...

給我的感覺好像是原作者認為傳遞給map，apply的函式才是更高階。我去wiki確認了一下：

In computer science, higher-order functions, are functions which do at least one of the following:

• take one or more functions as an input
• output a function

又去線上書店查了Errata，也沒找到相關資訊。

原作者的表述有錯嗎？我翻譯的時候該怎麼辦呢？