What is "stress" phonetically?

From Babylon English-English
Stress: emphasis, importance; accent, emphasis placed on a syllable of a word; pressure
Stress: subject to stress or strain; emphasize, accentuate
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From Farajbeik Farsi ( Windows Farsi )
Stress: فشار ، اهميت‌ ، تاكيد‌ ، تاكيد كردن‌
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From hFarsi - advanced version
Stress: فشار ، اهميت ،تاکيد کردن
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From HmT - English to Persian Glossary
Stress: اهميت، تاكيد، تاكيدكردن ، فشار
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From Salaty English-Farsi Dict. (Text ver.)
Stress: فشار ،اهميت‌ ، تاكيد ‌، تاكيد كردن‌

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From Farajbeik Farsi ( Windows Farsi )
Stress: فشار ، اهميت‌ ، تاكيد ، تاكيد كردن‌


From English Wikipedia

In linguistics, stress is the relative emphasis that may be given to certain syllables in a word, or to certain words in a phrase or sentence. The term is also used for similar patterns of phonetic prominence inside syllables. The word "accent" is often used with this sense, but it may be used for other kinds of prominence; stress specifically may thus be called stress accent or dynamic accent.
The stress placed on syllables within words is called word stress or lexical stress. The stress placed on words within sentences is called sentence stress or prosodic stress. The latter is one of the three components of prosody, along with rhythm and intonation.

Phonetic realization
The ways stress manifests itself in the speech stream are highly language-dependent. In some languages, stressed syllables have a higher or lower pitch than non-stressed syllables – this is called pitch accent (or musical accent). Other features that may characterize stressed syllables include dynamic accent (loudness), qualitative accent (differences in place or manner of articulation, typically a more peripheral articulation), and quantitative accent (syllable length, equivalent to agogic accent in music theory). Stress may be realized to varying degrees on different words in a sentence; sometimes the difference between the acoustic signals of stressed and unstressed syllables may be minimal.


Lexical stress
Lexical stress, or word stress, is the stress placed on a given syllable in a word. The position of lexical stress in a word may depend on certain general rules applicable in the language or dialect in question, although in some languages it is largely unpredictable, needing to be "learned" for each individual word.
Languages in which the position of stress in a word is less predictable are said to have variable stress. This applies to English and Russian, and to some extent to Italian and Spanish. Here stress is truly lexical: it must be memorized as part of the pronunciation of an individual word. In such languages stress may be phonemic, in that it can serve to distinguish otherwise identical words; for example, the English words insight and incite are distinguished in pronunciation only by the fact that the stress falls on the first syllable in the former and on the second syllable in the latter. Stress placement for some words may differ between dialects. For example, in British English the word labóratory is pronounced with primary stress on the second syllable, while American English stresses the first syllable, láboratory.


Levels of stress
Main article: Secondary stress
Some languages are described as having both primary stress and secondary stress. A syllable with secondary stress is stressed relative to unstressed syllables, but not as strongly as a syllable with primary stress. As with primary stress, the position of secondary stress may be more or less predictable depending on language. In English it is not fully predictable; for example, the words organization and accumulation both have primary stress on the fourth syllable, but the secondary stress comes on the first syllable in the former word and on the second syllable in the latter. In some analyses, for example the one found in Chomsky and Halle's The Sound Pattern of English, English has been described as having four levels of stress: primary, secondary, tertiary, and "quaternary", but these treatments often disagree with each other.
Peter Ladefoged and other phoneticians have noted that it is possible to describe English with only one degree of stress, as long as unstressed syllables are phonemically distinguished for vowel reduction. They believe that the multiple levels posited for English, whether primary–secondary or primary–secondary–tertiary, are mere phonetic detail and not true phonemic stress, and that often the alleged secondary stress is not characterized by the increase in respiratory activity normally associated with primary stress in English or with all stress in other languages.

the article is fine . but I prefer the last part of it
so if u can summarize it and emphasis on the last part I would be more thankful.