1. Tense Categories of the English Language

25.Stress patterns of the words in English
Stress is relevant to grammar as well as phonetics, since the stress patterns in some words may be affected by their grammatical word class. The verbs take the primary stress on the second syllable whereas the nouns and adjectives take it on the first syllable. There is often also some accompanying change in a vowel. (‘accent-ac’cent, ‘object-ob’ject, ‘record-re’cord). Several disyllables have the same stress pattern for both noun and verb or have a varying pattern; for example contact, contrast, comment. The present tendency seems to be to move the stress in disyllabic verbs of Latin origin to the first syllable. That tendency, which is also found in words of more than two syllables, whether they are verbs or nouns, is exemplified in the disputed pronunciations of contribute, controversy, dispute, distribute, research.


26.Historical development of the phonetic system of English
It took over two centuries (roughly 1450-1700) for English to acquire a stable spelling system. Starting in the fifteenth century and ending about 1600, a series of changes traditionally known as the Great Vowel Shift affected the long vowels. In Middle English the vowel sounds had Continental values, and the same letter was used to represent a short vowel and its corresponding long vowel; for example, the letter i was used for both the short vowel sound /i/ in present-day bit and the long vowel sound /i:/ in beet, but later i is also used as is a diphthong / ai.
One type of change that occurred during the seventeenth and eighteenth centuries was the loss of a sound in a cluster, resulting in a 'silent' letter in the spelling. The initial sounds in /kn/ and /gn/ were lost, so that k and g are not pronounced in words such as knee, kneel, knife, knight, knit, knob, knock, know, gnat, gnaw, gnome. Similarly, the w in wr is no longer pronounced in words such as wrap, wrestle, wrist, write, wrong. The sound of /l/ was lost in the modals should and would etc.
One significant change that affected some areas of the English-speaking world in the eighteenth century was the loss of the sound /r/ before a consonant or in final position, as in beard and beer. Accents that drop /r/ are called non-rhotic; those that retain /r/ are rhotic. Broadly speaking, non-rhotic accents are common in England and Wales and in most of the Commonwealth countries where English is the native language, whereas rhotic accents are common in the United States, Scotland, and Ireland.
The lost /r/ in non-rhotic accents reappears in certain environments when it is followed by a word beginning with a vowel, as in far away, for us, car engine
Another significant loss—the vowel in the regular verb inflection -ed— began to occur in late Middle English, but is not reflected in present-day spelling. The syllable /id/ is pronounced when the inflection follows /d/ or /t/ as in padded and trotted, but otherwise the vowel is dropped We therefore have three pronunciations for the -ed spelling: /id/, /d/ and /t/.