diff --git a/README.md b/README.md
index f0f76af7..d4cbf54d 100644
--- a/README.md
+++ b/README.md
@@ -87,7 +87,7 @@ Statements include:
 
 ## Functions
 
-Functions take arguments and produce a result. In MoonBit, functions are first-class, which means that functions can be arguments or return values of other functions. MoonBit's naming convention requires that function names should not begin with lowercase letters `[^a-z]`. Compare for constructors in the `Enum` section below.
+Functions take arguments and produce a result. In MoonBit, functions are first-class, which means that functions can be arguments or return values of other functions. MoonBit's naming convention requires that function names should not begin with uppercase letters (A-Z). Compare for constructors in the `enum` section below.
 
 ### Top-Level Functions
 
diff --git a/zh-docs/README.md b/zh-docs/README.md
index a6491139..a94a4cdc 100644
--- a/zh-docs/README.md
+++ b/zh-docs/README.md
@@ -85,7 +85,7 @@ fn init {
 ## 函数
 
 函数接受参数并产生结果。
-在 MoonBit 中，函数是一等公民，这意味着函数可以作为其他函数的参数或返回值。与下述的 `enum` 的类型构造子相对，MoonBit 的命名规则要求函数名不能以小写字母`[^a-z]`开头。
+在 MoonBit 中，函数是一等公民，这意味着函数可以作为其他函数的参数或返回值。与下述的 `enum` 的类型构造子相对，MoonBit 的命名规则要求函数名不能以大写字母 (A-Z) 开头。
 
 ### 顶层函数