Hi Mehvish, MARC is, unfortunately, a really difficult data format to understand without any library science background. The numbers are fields like author name, title statement, and subject while the letters prefixed with some symbol (often $, but ‡ is used too) is a subfield. So a 245 title field has title subfield $a, subtitle subfield $b, author statement $c, etc. The cataloging editor does link to some documentation but you can use the OCLC or Library of Congress sites to read more about field meanings: https://www.loc.gov/marc/bibliographic/ https://www.oclc.org/bibformats/en/about.html To answer your specific question about language codes, here's a quote from OCLC: - A single language code may be insufficient to describe the language of an item. If the item is multilingual or a translation, use multiple language codes. Enter the first code in Lang. Enter the multiple codes (including the first code) in field 041 (Language Code). - Use the predominant language code for a multilingual item that has two to six languages. If predominance cannot be determined, use the code that is first alphabetically. If the multilingual item has more than six languages, use the code for the language of the first title in field 245. If the item is multilingual with no predominant language and the cataloging institution has chosen not to specify a language, use code *mul*. https://www.oclc.org/bibformats/en/fixedfield/lang.html is the page where I found that. Hope that's helpful, good luck with your cataloging! Best, Eric Phetteplace Systems Librarian California College of the Arts libraries.cca.edu | vault.cca.edu 510.594.3660 2>/dev/null