Dash Dash The dash is a punctuation mark that is similar in appearance to and , but differs from these symbols in both length and height. The most common versions of the dash are the en dash (–), equal to half the height of the font; the em dash (—), twice as long as the en dash; and the horizontal bar (―), whose length varies across typefaces. Historically, the names of en dash and em dash were loosely related to the width of a lower-case "n" and upper-case "M", respectively, in commonly used typefaces. Usage varies both within English and in
Phonological rule (in "buses"); these forms are all theorized to be stored mentally as the same "-s", but the surface pronunciations are derived through a phonological rule. In most dialects of American English, speakers have a process known as intervocalic alveolar flapping that changes the consonants /t/ and /d/ into a quick flap consonant ([ɾ] in words such as "butter" () and "notable" (). The stop consonants /t/ and /d/ only become a flap in between two vowels, where the first vowel is stressed and the second is stressless. It is common to represent phonological rules using formal rewrite rules in the