The word 相似 is formed by combining two independent characters, each contributing a core meaning that together create a new, unified concept. The first character, 相 (xiāng), carries the fundamental idea of "mutual" or "each other", implying a reciprocal relationship. The second character, 似 (sì), means "to resemble" or "to be like". When joined, they create a compound where 相 intensifies and formalizes the relational aspect of 似, producing the complete notion of "mutual resemblance", that is, the state of two or more things being alike or similar to one another.