这个符号是用来划分音节的，术语：音节化（Syllabification），至于wary为啥会分成war|y，请看Wikipedia English phonology条目：
According to one view, English is unusual in this regard, in that stressed syllables attract following consonants, so that ˈCVCV and ˈCVCCV syllabify as /ˈCVC.V/ and /ˈCVCC.V/, as long as the consonant cluster CC is a possible syllable coda; in addition, /r/ preferentially syllabifies with the preceding vowel even when both syllables are unstressed, so that CVrV occurs as /CVr.V/. However, this view is not widely accepted, as explained in the following section.
However, possibly due to the weak correspondence between sounds and letters in the spelling of modern English, written syllabification in English is based mostly on etymological or morphological instead of phonetic principles. For example, it is not possible to syllabify "learning" as *lear-ning* according to the correct syllabification of the living language. Seeing only *lear-* at the end of a line might mislead the reader into pronouncing the word incorrectly, as the digraph *ea* can hold many different values. The history of English orthography accounts for such phenomena.