What belongs in an abstract?
The abstract must provide a summary of the problem addressed by the study, a brief description of methodology, a clear statement of results, and a brief conclusion of the most important results that directly relate to your aims. Simply, an abstract should contain a sentence or two of each section of a journal article (introduction, methods, results, discussion), but should not go into the detail that the rest of your article will contain.
In general, abstracts should avoid or limit the use of abbreviations. References and diagrams should not be shown in the abstract. Additionally, abstracts should avoid the use of jargon and slang, as the abstract must be able to stand alone from the text. Grammar and sentence structure should be free from errors. In most cases, the abstract should be written in the past tense, except for the introductory sentence or sentences that describe the paper's aim.
Some journals, such as the American Journal of Botany, the Journal of Ethnobiology and Ethnomedicine, and others, require an abstract to be demarcated with headings, which are specified by the journal. For example, the American Journal of Botany requires an abstract written with the following sections: Premise of the Study, Methods, Key Results, Conclusion.