Thx Gareth! I’m still trying to figure out the last example! When I learn the right sentence of “It is as similar as…” rather than “They are as similar as the lion…”, I feel different to link it to the explanation before that. For me, it is also related to another question, “same” normally doesn’t come with “to”, but why? Like you mentioned, X and Y are reciprocal relationships, “same” and “similar” are expressions for relationship, one thing cannot stand when talking about this feature sharing. “with” is even not accepted by these two words when X figuratively share the “same” or “similar” (attributes) with Y. Cheers!

There are often several ways to say a sentence. You can also say similar as for example... I found this... When we say "X is as powerful as Y", it means that X and Y are equally powerful. By the same token, "X is as similar as Y" would mean that X and Y are equally similar. However it does not make sense to say that two things are "equally similar" to each other, since similarity is a reciprocal relationship. It is possible, in the right context, for two things to be equally similar to a third thing, e.g.: A: How similar is the tiger to the leopard? B: It's as similar as the lion we just saw.