點解要加to在belong和 me中間

belongs to 係一定要一齊用, 你就當 belongs 係"屬"咁解, to 係"於"咁解好了~ 屬於係一個詞語嘛!

因為這是 Phasal Verb, 所以要死記.

-to- is -belong-'s preposition. -belong- is always followed by -to-, no matter if -me- is used or not, so you can't omit it.