First indicator - Level of subject

#  No information provided

0  No level specified  [Not used]

1  Primary  [NLM use only]

2  Secondary  [NLM use only]

Second indicator - Thesaurus

0  Library of Congress Subject Headings

1  LC subject headings for children's literature

2  Medical Subject Headings

3  National Agricultural Library subject authority file

4  Source not specified  [Not used]

5  Canadian Subject Headings

6  Répertoire de vedettes-matière

7  Source specified in subfield $2


a  Topical term or geographic name entry element (NR)

b  Topical term following geographic name entry element (NR)  [Not used]

c  Location of event (NR)  [Not used]

d  Active dates (NR)  [Not used]

e  Relator term (R)  [Not used]

g  Miscellaneous information (R)

v  Form subdivision (R)

x  General subdivision (R)

y  Chronological subdivision (R)

z  Geographical subdivision (R)

0  Authority record control number or standard number (R)

2  Source of heading or term (NR)

3  Materials specified (NR)

4  Relator code (R)

6  Linkage (NR)

8  Field link and sequence number (R)

NOTE:  See MARC 21 Format for Bibliographic Data (650 Subject Added Entry - Topical Term) for code definitions not given below.


Field 650 contains all subject headings not belonging to the other categories, including:

1.   General terms of the type included in the LC list of subject headings, e.g., "Dogs," "Chemistry," etc.

2.   Systematic names of families, genera, and species in botany and zoology, and chemical compounds.

3.   Names of events and holidays, e.g., Tannenberg, Battle of, 1914; Phoenix Part Assassination, 1882.

4.   A wide variety of names or terms applied to individual objects, or classes of objects, e.g.,

Neo (Artificial language)

AUNTIE (Computer system)

Canadian intelligence test

Rolls-Royce automobile

EXCEPTION:  When a subject heading consists of a personal name in catalog entry form followed by the phrase "in fiction, drama, poetry, etc.," treat the name as a personal name and assign tag 600.

5.   Names of deities, fictional and mythological characters, etc. not capable of authorship.

Second indicator

The second indicator describes the source of the heading.  For instructions see Subject Headings - General Information.


For a description of subfields $v, $x, $y, $z, and $2, see Subject Headings - General Information.

650 #0 Zoology $z Costa Rica $z Cocos Island.

650 #0 Art, Modern $y 19th century $x History $v Periodicals.

650 #0 Red Wing Potteries Strike, 1967.

650 #3 Cosmochemistry $v Periodicals.

650 #0 Banks and banking $z Israel $v Statistics.

650 #6 Guerre, 1939-1945 (Mondiale, 2e) $x Historie des régiments $z Canada.

650 #2 Medicine $v periodicals.

650 #2 Allied Health Personnel $x education $z United States $v directories.

Related fields, etc.

Subject Headings - General Information, Appendix I

650 Subject Added Entry - Topical Term  (MARC 21 Format for Bibliographic Data)

See also:

6XX  Subject Access Fields

Variable Data Fields

Section E.  MARC 21 Format for Serials as Applied Within CONSER

CONSER Editing Guide:  Contents