| Item | Keyword searching | Searching with Subject Headings |
| Who chooses the search terms? | You do! The words you use may happen to be the same as subject headings, or they may be different. | The creators of the database decide on the terminology when they develop their thesaurus. Then you select terms from their thesaurus with which to run your search. |
| Automatic inclusion of synonyms and related terms? | Nope! The system searches only for an exact match, and does not have the ability to search on synonyms/related terms. | Yes. The system automatically searches on close synonyms or related terms. In addition, it has the ability to search on more specific terms. |
| Number of results |
Often very large numbers because the system brings up every record that contains that word, even if it is an incidental usage. |
Often smaller numbers because the system only brings up records to which the Subject Heading has been deliberately assigned. |
| Accuracy |
Can be quite low because the system cannot differentiate between an incidental usage of a term and when an article is actually about that topic. |
Often highly accurate and very focused because only records to which the Subject Heading has been assigned will come up. |
| Flexibility |
Very flexible! You can use any term you want. However, the flip side is that you must conduct separate searches on every possible variation of the term. |
Somewhat. You can only choose from the list of Subject Headings in the database thesaurus. |
| Special database requirements | None! Most databases can accommodate keyword searches. | In order to search with Subject Headings, the database must employ a thesaurus. If there is no thesaurus, then a keyword search is the only option. |
| Best used when … | … you are trying to conduct a very thorough search and are looking for a needle in a haystack. Also when searching on brand new topics not yet represented in the thesaurus; jargon; proper names; brand names; some gene and protein names, etc.,. | … you want to conduct an efficient, highly focused search from which a high percentage of results will be relevant. |
| Not so good when … | … you want to conduct an efficient, highly focused search from which a high percentage of results will be relevant. | … you need to search on brand new topics not yet represented in the thesaurus; jargon; proper names; brand names; some gene and protein names, etc., |