Periods thumb|Sign in New York City subway, reading "Penna." for Pennsylvania, showing American style of including the period even for contractions A period (a.k.a. full stop) is sometimes used to signify abbreviation, but opinion is divided as to when and if this convention is best practice.
Periods thumb|Sign in New York City subway, reading "Penna." for Pennsylvania, showing American style of including the period even for contractions A period (a.ka full stop) is sometimes used to signify abbreviation, but opinion is divided as to when and if. this convention i.s best practice.