I agree with Akkur but let me add that the abstract is generally limited to a word count (75 words/150 words) while your conclusion is not (unless they ask for a word limited conclusion at beginning of article.  It is important in the abstract to use key words and to state the nature of the article (objective/hypothesis) from the very beginning of the abstract.

Dear Saifeldin, abstract should attract and interest the reader underlining main topics that are covered in the paper, while conclusion sums up all research. 

An abstract and conclusion are one of the main parts of a scientific publication, but the content is different, namely ::

Abstract is the statement of what a scholarly or complex written work contains, presented as a summary usually by someone other than the author of the work. An abstract aims to present only the gist of the subject matter, stresses brevity, and makes no attempt to preserve the flavor or style of the original. You can see also abridgment, digest, outline, précis, summary, and synopsis to undesrand better than now.

While a conclusion is the last part of something, its end or result. When we/you/they write a scientific paper, we/you/they always end by summing up our/their arguments and drawing a conclusion about what we/you've been writing about. The phrase in conclusion means "finally, to sum up," and is used to introduce some final comments at the end of a speech or piece of writing. The phrase jump to conclusions means "to come to a judgment without enough evidence". A foregone conclusion is an outcome that seems certain.

Abstract is the summary of the entire conduction of the study including the background, objective, methodology, results and the conclusion. Abstract could be structured or unstructured.

The conclusion is extracts of the main findings of the study, including the main message, recommendation or lesson that represents authors understanding of the results based on critical analysis.    

Abstract is a summary of the purpose, methodology and results of the research. Findings are the conclusions reached after investigating the hypothesis of the research.

Abstract gives the whole idea about your work but conclusion only includes the summary and recommendations from your results with future directions of the research.

Dear colleagues

thank you very much for your respond to my question and for the valued information and ideas about Abstract and Conclusion you provide.  

Here's a link to writing the structured abstract, which is very much needed in journals today.

Debra

http://files.eric.ed.gov/fulltext/EJ727552.pdf

 .... others ...

Abstract is polls of a goal post and conclusion is a net with something

Abstract is written at the beginning, conclusions at the bottom

In common parlance .....Abstract is the ESSENCE while Conclusion is JUSTIFICATION

Abstract is a summary of any research work but while writing an article / research paper it should be written after one pens down complete article. This helps a lot in summarizing the research work in short. Conclusion is finding of your work at the end and should include drawbacks and need for further research on the same topic if any. 

Abstract is a resumed of the work. Conclusion is the novelty of the consequences of the work.

hi. in conclusion , the researcher should explain the theoretical and practical implications of the results and findings of the study in detail. focusing on further suggestions and study limitations is a component of conclusion. conclusion is interpreting the results considering the studies cited in review of literature agreeing or disagreeing their views based on the new findings. abstract is the gist of the study with more introduction or background knowledge , niche, aim and results. best

In a piece of writing what is the difference between abstract and conclusion?

There is a subtle difference between the two. Abstract is the summary of salient points of your research which might include problem statement, research rationale, method, findings etc. as well as conclusion in a format with limited word counts. Its objective is to enable readers to gain general idea about your research & attract them to read on.

Whereas conclusion is the last section of your research write up detailing the closing remark of your research. Some authors also use conclusion section to share their research limitation & future recommendation which are important for future researchers to continue their further research.

C. Lewis Kausel gave a direct and simple answer.

abstract is summery ( khulasa in urdu and Mukhallas in arabic) whereas conclusion is the result of our study after data analysis and discussion.

Abstract is the summary of the article. It is much like an advertisement of the paper. It includes the most important information. Abstract will include background, important findings and also what the paper aims to achieve. Conclusion is the part where you summarize what the paper has already achieved. It includes all the findings, recommendations and future scopes of the work. It is a little bit more detailed in terms of information compared to abstract. In a nutshell, a conclusion gives completeness to a research article whereas the abstract merely summarizes it.

Abstract is referred to the summary the work and mentioned to the aim, the method that performed . and the past tens is always used to write it .....

But conclusion is mentioned to the main discussion for the important parts of interpenetration of results and any strange or new analysis....

I agree with all. Very reach answers.

Abstract holistically but in fewer word count succinctly sums up A-Z about the research. On the other hand, conclusions highlight the findings in line with the study's objectives.

In simplified answer, the abstract must include the conclusions.

Yes..agreed with your answer Dr.Naseer.

Yes, good question and agree with Dr. C. Lewis Kassel.

I agree with Dr. Akkur Chandra Das and Dr. Jack S Damico explanations.

Abstract should be a summery of the manuscript.

Conclusion should point out the most important results.

I fully agree with all my colleagues' answers especially both Dr. Akkur Chandra Das & Dr. Jelena B Popović-Djordjević