gcc can't find `FT_Error_String` when trying to compile

I am trying to compile an application that uses freetype2, I downloaded and compiled the latest version of freetype2 from an official site.
I compile the program using this command:

gcc ttf2sfn.c -I/home/emilia/os/freetype-2.10.1/include -L/home/emilia/os/freetype-2.10.1/objs -lfreetype

However, the linker cannot find the `FT_Error_String' character.
It prints this error message:

/tmp/cc6FGxyc.o: In function `main':ttf2sfn.c:(.text+0x25aa): undefined reference to `FT_Error_String'ttf2sfn.c:(.text+0x352c): undefined reference to `FT_Error_String'collect2: error: ld returned 1 exit status

Why is this happening?Thanks.