Two problems about the basic knowledge of English

First of all, phoneme is the smallest phonetic unit divided from the perspective of sound quality, which can be divided into two categories from the pronunciation characteristics, namely vowel phoneme and consonant phoneme. The air flow comes from the lungs, and it can be exhaled freely through the mouth, and the vocal cords vibrate, so the sound is vowels. Such as /a/, /i/, and so on. The airflow exhaled from the lungs, passed through the mouth, and was blocked at a certain position, so the sound made was a consonant. Such as b, p, etc. People use these phonetic symbols to represent the pronunciation of 26 letters.

Secondly, generally speaking, a syllable must contain a vowel, which can be a vowel, a vowel with a consonant, or a vowel with multiple consonants, such as sci-en-? ti-fic /，sai-？ The word n-' ti-fik/ has four syllables, separated by a space symbol. But in special cases, consonants can also form syllables, that is, words ending in consonants /l/, such as ta-ble/'tei-bl/, apple, etc.

Of course, syllables are composed of phonemes, but they are expressed in the form of letters in writing. Syllables are only spoken forms, and letters are the carriers of syllables. When we say that tea is pronounced as /ti:/, we just express this phoneme combination.

About your four points, 1. Syllables are characterized by vowels, which can form a syllable, just as initials and finals in Chinese form a pinyin. Vowels are the main body of syllables, and consonants are the boundaries of syllables. 2. A word can have multiple syllables, and each syllable is a collection of vowels and consonants, such as con-gra-tu-la-tion[k? n-？ ɡr？ -tju-？ The word lei-n] has five syllables, which can be considered to be divided by vowels, because each syllable has a vowel. I don't understand what you mean. Does it mean that the stressed opening syllable can only form a syllable with the preceding consonant? Such as' stu-dent/'stju:d? Nt/ here /ju:/ is a stressed syllable, which can only form a syllable with the preceding /st/ and cannot be read with the following /d/. 4. Closed syllables: syllables that end with one or more consonants (except R) and have only one vowel letter in the middle, such as sit and shout. In stressed closed syllables, vowels are pronounced as short vowels. For example, in for-'get, be-'gin, /'get/, /'gin/ means to stress closed syllables. Open syllable: 1) A monosyllable ending in a pronounced vowel. Example: yes, he. 2) syllables ending in consonants (except r)+silent e. Example: make, like. Vowel letters are pronounced by letter names in stressed open syllables. In the contract [k? n-？ ɡr？ -tju-？ Lei-n], where/? Lei/ is a stressed syllable and an open syllable, so this syllable is a stressed open syllable, and the second A here is the pronunciation of the alphabet and the U in the student. Actually, it depends on their phonetic symbols here. Syllables refer to phonetic symbols, but they are expressed in the form of letters in words. Meanwhile. In fact, there is no need for teachers to recite the phonetic symbols of letters or letter combinations in order to let everyone read words quickly. Just read the phonetic symbols of words and slowly develop a sense of language. Rote memorization is really mechanical, and confusion is not a shortcut. Memorizing words and phonetic symbols is the best way, there is no shortcut, this is the experience of people who have experienced it. But your curiosity is commendable ~ ~ ~