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equal; identical; the same
no different (from); just like; equivalent
二つのグループの人数は斉しい。
The two groups have an equal number of people.
両チームの実力はほぼ斉しかった。
The two teams were nearly equal in ability.
条件が斉しくないと正確に比較できない。
You can't compare accurately if the conditions aren't equal.