Elucidatory is the rare, formal adjective: describing something that helps explain a hard point by giving more information — an elucidatory remark, an elucidatory footnote, an elucidatory example. It does not mean the speaker is explaining right now (that would be the verb elucidate); it means the comment, note, or diagram is there in order to make things clearer.

elucidatory is the rare, formal adjectiveelucidatory是個少見、正式的形容詞 describing something that helps explain a hard point by giving more information用來形容某樣東西透過提供更多資訊來幫助解釋一個難懂的地方 — an elucidatory remark, an elucidatory footnote, an elucidatory example——像an elucidatory remark、an elucidatory footnote、an elucidatory example it does not mean the speaker is explaining right now它不是指說話的人現在正在解釋 (that would be the verb elucidate)（那是動詞elucidate的意思） it means the comment, note, or diagram is there它是指那則評論、註記，或圖表存在的目的 in order to make things clearer是為了讓事情更清楚

You will almost only meet it in academic or legal prose. Though actually, even there many writers prefer explanatory or clarifying, which students can use with a much quieter conscience.

you will almost only meet it in academic or legal prose你幾乎只會在學術或法律文章裡遇到它 though actually不過其實 even there many writers prefer explanatory or clarifying即使在那裡，很多作者也比較喜歡用explanatory或clarifying which students can use with a much quieter conscience學生用這兩個字心裡會踏實得多

If you never need this adjective, that is not a gap in your English.

if you never need this adjective如果你從來用不到這個形容詞 that is not a gap in your English那不代表你的英文有缺口