What Dewey decimal classification system is dictionary including thesaurus?

A dictionary, including a thesaurus, would fall under the Dewey Decimal Classification (DDC) number 423.

Here's why:

* 400: This is the main category for language.

* 420: This is the subcategory for English language.

* 423: This is the specific category for dictionaries and lexicons, which includes thesauruses.

So, a dictionary with a thesaurus would typically be classified under 423.