It's not an error. From the preface of the dictionary:

(1)

 

한자의 원래 음과 한글 표기로 제시되는 음이 다른 경우에는 해당 한자 오른쪽에 '▽' 기호로 표시하였다. 그러나 사이시옷이 첨가된 형태나 어문 규정의 차이로 달리 표기한 북한어에는 표시하지 않았다.

 

<예>
시월01 (十▽月) , 찻-잔 (茶盞), 페경지(廢耕地)

Roughly translated, it says:

When the original sound of the hanja and the sound that is expressed using Hangul does not match, the '▽' symbol is used to mark such cases. However, forms with 사이시옷 and North Korean words which follow different set of orthography rules are not marked.

These irregularities are due to historical sound changes.

Some other important dictionary symbols:

• ▼ is used to mark that the word in the original language is nonexistent.

• - (a hyphen) is used at the border of morphemes in compound words. You should never put a space instead of the hyphen when using that word.

• ^ is used when spacing is optional.

It's not an error. From the preface of the dictionary:

(1)

한자의 원래 음과 한글 표기로 제시되는 음이 다른 경우에는 해당 한자 오른쪽에 '▽' 기호로 표시하였다. 그러나 사이시옷이 첨가된 형태나 어문 규정의 차이로 달리 표기한 북한어에는 표시하지 않았다.

<예>
시월01 (十▽月) , 찻-잔 (茶盞), 페경지(廢耕地)

Roughly translated, it says:

When the original sound of the hanja and the sound that is expressed using Hangul does not match, the '▽' symbol is used to mark such cases. However, forms with 사이시옷 and North Korean words which follow different set of orthography rules are not marked.

These irregularities are due to historical sound changes.

Some other important dictionary symbols:

• ▼ is used to mark that the word in the original language is nonexistent.

• - (a hyphen) is used at the border of morphemes in compound words. You should never put a space instead of the hyphen when using that word.

• ^ is used when spacing is optional.

It's not an error. From the preface of the dictionary:

(1)

한자의 원래 음과 한글 표기로 제시되는 음이 다른 경우에는 해당 한자 오른쪽에 '▽' 기호로 표시하였다. 그러나 사이시옷이 첨가된 형태나 어문 규정의 차이로 달리 표기한 북한어에는 표시하지 않았다.

<예>
시월01 (十▽月) , 찻-잔 (茶盞), 페경지(廢耕地)

Roughly translated, it says:

When the original sound of the hanja and the sound that is expressed using Hangul does not match, the '▽' symbol is used to mark such cases. However, forms with 사이시옷 and North Korean words which follow different set of orthography rules are not marked.

It's not an error. From the preface of the dictionary:

(1)

한자의 원래 음과 한글 표기로 제시되는 음이 다른 경우에는 해당 한자 오른쪽에 '▽' 기호로 표시하였다. 그러나 사이시옷이 첨가된 형태나 어문 규정의 차이로 달리 표기한 북한어에는 표시하지 않았다.

<예>
시월01 (十▽月) , 찻-잔 (茶盞), 페경지(廢耕地)

Roughly translated, it says:

When the original sound of the hanja and the sound that is expressed using Hangul does not match, the '▽' symbol is used to mark such cases. However, forms with 사이시옷 and North Korean words which follow different set of orthography rules are not marked.

These irregularities are due to historical sound changes.

Some other important dictionary symbols:

• ▼ is used to mark that the word in the original language is nonexistent.

• - (a hyphen) is used at the border of morphemes in compound words. You should never put a space instead of the hyphen when using that word.

• ^ is used when spacing is optional.