The ancients used the method of backcutting to mark the pronunciation, and the specific information can be more detailed. There is only one simple explanation:
Reverse cutting is a phonetic notation method created by the ancients after "pronunciation" and "reading if". The basic rule is to put two Chinese characters together to phonetic a word, cut the word to take the initial consonant, and cut the word to take the vowel and tone.
Examples: publication (bitter cold cutting), altar (dry cutting);
Here, bitter and disciple are the upper characters, taking their initials K and T, cold and dry as the lower characters, and taking their vowel an and tone (the tone in ancient times is different from today's), which can be put together normally;
Therefore, as long as you master a certain number of upper and lower words as the basis, you can form the basis of spelling learning (a more detailed list of upper and lower words can be further understood on the Internet)
I wish you a happy study.