There are two categories of words here: 1) 三叉路, 叉焼, 音叉 and 2) 夜叉.
In the first category, 叉 is used for its semantic value: a fork. In 三叉路, this is a path or road that branches in three directions like the shape of a Y. In 叉焼, it is the pronged fork that the pork is attached to for cooking. In 音叉, it is the U-shaped fork used in tuning sounds.
As for the second category, it has nothing to do with the semantic meaning of the character but rather the phonetic value. In 夜叉, it is being used to transliterate the Sanskrit word yakṣa (यक्ष).