I need a dictionary definition and APA reference for mental concentration
You can get a definition for "concentration" from our Oxford English Dictionary database. You find it by clicking on the Databases link on the library's homepage. Do your search for just concentration as that is the word you need. The mental part is implied and is part of the definition you will find. Also, look toward the upper right of the entry and you will be able to click on Cite to get the APA citation.