750 Index Term - Topical

Field definition and scope:

Field 750 contains a topical term used as an index term that supplements terms derived from data in the MARC classification record. The term may be referred to in the classification number and caption in field 153 (Classification Number).

The field may be used to link a classification number with a related controlled subject heading. Topical index terms may consist of general subject terms including names of events or objects. The 750 field provides access to classification numbers according to generally accepted thesaurus-building rules [e.g., Library of Congress Subject Headings (LCSH), Medical Subject Headings (MeSH)]. The values in the second indicator position or the data in subfield $2 (Source of heading or term) identify the subject heading system or thesaurus used by an institution to formulate the topical index term. To be included in this field, a topical index term must match the controlled heading, including any subdivisions. Index terms not controlled by a thesaurus are contained in field 753 (Index Term - Uncontrolled).

Field 750 is repeatable.

Guidelines for applying content designators:

Field 750 parallels the 650 Subject Added Entry field in the bibliographic format. The indicators and subfield codes below were created from the information in field 650. Examples of field 750 are provided in this section. Guidelines for the input conventions and the source for the content designators are in MARC 21 Format for Bibliographic Data: 650 (Subject Added Entry - Topical Term).

For indicator and subfield code definitions and examples, and designator repeatability, see table below:

Position	Description	Repeatability
Field 750	Index Term - Topical	R
Indicator:
First	Level of subject
#	No information available
0	No level specified
1	Primary subject
2	Secondary subject

Second	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
5	Canadian Subject Headings
6	Répertoire des vedettes-matière
7	Source specified in subfield $2

Subfield code:
$a	Topical term or geographic name entry element	NR
$b	Topical term following geographic name entry element	NR
$c	Location of event	NR
$d	Active date	NR
$i	Explanatory text	R
$v	Form subdivision	R
$x	General subdivision	R
$y	Chronological subdivision	R
$z	Geographic subdivision	R
$0	Authority record control number or standard number	R
$1	Real World Object URI	R
$2	Source of heading or term	NR
$3	Materials specified	NR
$6	Linkage	NR
$8	Field link and sequence number	R

See: Examples for this field.

Content designator history:

Subfield $0 - Record control number [redefined, 2010]

Subfield $1 - Real World Object URI [new, 2017]