4xxx

4xxx is a string representing a four-digit number whose thousands digit is 4. In technical writing and data modeling, this form is commonly used as a placeholder to indicate a value within a known range without specifying the exact digits. The convention implies numbers from 4000 through 4999, depending on whether the trailing digits are constrained by the context.

Because many industries use numeric prefixes to classify items, 4xxx is frequently encountered in product catalogs, part numbers, and model designations. In these settings the prefix signals a particular family or generation within a broader line, but there is no universal meaning; the interpretation varies by supplier.

In documentation and testing, 4xxx may be used to represent sample data or to anonymize sensitive numeric identifiers. It helps illustrate data structures or interfaces where a four-digit numeric field is required, without exposing specific values.