Seminar №2 Word-formation in Modern English

'absent a ↔ ab'sent v; 'frequent a ↔ fre'quent v;
'perfect a ↔ per'fect v; 'abstract a ↔ ab'stract v.
This stress distinction is, however, neither productive nor regular. There are many denominal verbs that are forestressed and thus homonymous with the corresponding nouns. For example, both the noun and the verb comment are forestressed, and so are the following words: exile, figure, preface, quarrel, focus, process, program, triumph, rivet and others.
There is a large group of disyllabic loan words that retain the stress on the second syllable both in verbs and nouns: accord, account, advance, amount, approach, attack, attempt, concern, defeat, distress, escape, exclaim, research, etc.
It is worth noting that stress alone, unaccompanied by any other differentiating factor, does not seem to provide a very effective means of distinguishing words. And this is, probably, the reason why oppositions of this kind are neither regular nor productive.