等しい

1. Origins, structure, and basic meaning

• Structure: 等しい, read ひとしい, joins the equality stem 等し with the i-adjective ending い.
• Basic usage: Use it when two compared objects have equal quantity, value, or conditions, as in 長さが等しい.

2. Common pitfalls and similar expressions

• Grammar and combinations
  • It expresses equality under a particular criterion more than identity of the objects themselves with 同じ.