制定, 改定, and 改訂: Establishing rules and revising different objects
Compare establishing rules, revising fees or terms, and revising guides or dictionary editions. The object helps distinguish the two spellings read かいてい.
Establishing a new rule
制定 means enactment or establishment. 「町は新しい景観条例を制定した。」 reports a town enacting a new landscape ordinance. The ordinance is the stated object.
「規則の制定に先立って住民の意見を聞いた。」 describes hearing residents’ opinions before establishing the rules. The completed consultation does not itself report completed enactment.
Revising an existing standard or fee
改定 means revision or amendment. 「利用規約が来月から改定される。」 says the terms of use will be revised next month. The revision is future.
「委員会は料金の改定を正式に決めた。」 reports the committee formally deciding to revise fees. A decision about a fee change is distinct from fees having already changed.
Revising a publication
改訂 means revision. 「制度の変更に合わせて手引きを改訂した。」 reports revising a guide to reflect a system change. The revised object is the guide.
「辞書の改訂版には新しい用例が加えられた。」 says new usage examples were added to a revised dictionary edition. 改定 and 改訂 share a reading, but their objects differ here; change size versus typographical corrections is not a fixed division.
Which spelling of かいてい fits revising fees, and which fits a dictionary edition with new usage examples?
Show the answer and why
Fee revision connects with 改定, while the revised dictionary edition connects with 改訂. The object being changed, rather than change size or typographical errors alone, clarifies the spelling.