One of the most common abbreviation mistakes that new writers make, especially when penning academic papers, is the Latin phrase et al. Part of the problem is that we don’t know Latin; another part is that neither do our computer spell checkers.

Et al. means “and others”. Et is Latin for “and” while alii is Latin for “others”. In modern English, we don’t abbreviate et but we do abbreviate alii to al. Because of this, the correct way to spell et al. is with one period after the l, as in: Boston et al. found that hiking just 20 minutes a day can change a person’s mood for the better.

Sometimes writers will forgo the period after the last l, but for academic papers written in APA style, it is required. A few spell check programs will flag this as an error, however, so watch for it.