Sentence:  Donegan (1985: 37–38) offers the following description of <WSD>fortitions</WSD> and lenitions. <WSD>Fortitions</WSD> are listener-oriented processes, which increase phonetic properties of phonemes. They strengthen the properties of an individual segment by emphasizing certain phonetic features, sometimes at the expense of other features within the segment. 
Meaning of the word marked with <WSD> tags:  A sound change in which a consonant becomes more fortis.