stressed syllable

You must study phonetics. There are some rules about which syllable to stress. But...the rules are rather complicated! Probably the best way to learn is from experience. When you learn a new word, you should also learn its stress pattern. If you keep a vocabulary book, make a note to show which syllable is stressed. If you do not know, you can look in a dictionary. All dictionaries give the phonetic spelling of a word. This is where they show which syllable is stressed, usually with an apostrophe (') just before or just after the stressed syllable. (The notes at the front of the dictionary will explain the system used.) Look at (and listen to) this example for the word plastic. There are 2 syllables. Syllable #1 is stressed.

PLAS TIC---/plæs'tIk/

There are two very simple rules about word stress:

One word has only one stress. (One word cannot have two stresses. If you hear two stresses, you hear two words. Two stresses cannot be one word. It is true that there can be a "secondary" stress in some words. But a secondary stress is much smaller than the main [primary] stress, and is only used in long words.) We can only stress vowels, not consonants.

1 Stress on first syllable

rule example
Most 2-syllable nouns PRESent, EXport, CHIna, TAble
Most 2-syllable adjectives PRESent, SLENder, CLEVer, HAPpy

2 Stress on last syllable

rule example
Most 2-syllable verbs to preSENT, to exPORT, to deCIDE, to beGIN
 

3 Stress on penultimate syllable (penultimate = second from end)

rule example
Words ending in -ic GRAPHic, geoGRAPHic, geoLOGic
Words ending in -sion and -tion teleVIsion, reveLAtion

4 Stress on ante-penultimate syllable (ante-penultimate = third from end)

rule example
Words ending in -cy, -ty, -phy and -gy deMOcracy, dependaBIlity, phoTOgraphy, geOLogy
Words ending in -al CRItical, geoLOGical

5 Compound words (words with two parts)

rule example For compound nouns, the stress is on the first part BLACKbird, GREENhouse For compound adjectives, the stress is on the second part bad-TEMpered, old-FASHioned For compound verbs, the stress is on the second part to underSTAND, to overFLOW

Most spoken languages will stress a syllable in each word. That is, rather than using a monotone to deliver all syllables, one syllable in each word is emphasized.

Unfortunately, unlike a language like Spanish which uses a handful of predictable rules to determine the stressed syllable in each word, English is chaotic.

Here is a link to a web page that discusses the stress "rules" for English: http://www.englishclub.com/pronunciation/word-stress-rules.htm

It must be understood that these are not really rules, but generalizations. For each "rule", there are many, many exceptions. 

A good dictionary will have a pronounciation guide for each word. Such a guide will help you understand which syllable is stressed in each word.

stess on the word delicious