Two Latin abbreviations tell your readers you are offering only a partial list: et al. and etc.
Use et al. for citing four or more people. (A memory trick: et al. rhymes with y’all — and y’all has a similar meaning.)
It’s known that the cognitive talents underlying voice perception, such as speaker recognition, are shared with many other animal species, but the findings of Petkov et al. provide a cerebral location for these abilities.
“Monkeys Hear Voices” ScientificAmerican.com
More “Monkeys Hear Voices”: this time the et al. is as an MLA in-text citation:
Speaking in languages rather than relying solely on vocal sounds for communication has long been believed to set humans apart from animals. However, recent research has determined that having an area of the brain devoted to processing voices is not uniquely human (Petkov et al. 367-374).
Using etc. tells readers your list of things could continue beyond the items you have mentioned. (If your list is people, however, remember to use et al. instead.) Save etc. for casual writing since few instructors allow it in homework or papers.
This quote comes from a 2009 interview in Scientific American with Daniel Tammet, who “holds the European record for reciting the first 22,514 decimal points of the mathematical constant Pi” from memory:
The concept [of intelligence] is a useful and important one, for scientists and educators alike. My objection is to thinking that any “test” of a person’s intelligence is up to the task. Rather, we should focus on ensuring that the fundamentals (literacy, etc.) are well taught, and that each child’s diverse talents are encouraged and nourished.
Did you notice? The “et” of et al. does not get a period because it is a full word. Finally, even though they are derived from foreign phrases, italics are not used for et al. or etc. in MLA or APA formatted essays.