Sentence:  In order to distinguish between the two kinds of voiceless final stops the terms 'final devoicing' and <WSD>'fortition</WSD> after sonorants' are used here. Although <WSD>fortition</WSD> after sonorants is quite well attested for present-day contact English and in general Irish English, the significance of "fent", "spent", "trent" in terms of interference is slight as <WSD>fortition</WSD> after /n/ is common in mainland varieties of Middle English as well. Especially in late Middle English many instances of a preterite in /d/ after /n/ changing to /t/ with simultaneous loss of the preterite ending are recorded. 
Meaning of the word marked with <WSD> tags:  A sound change in which a consonant becomes more fortis.