The outward expression of Bina - the Intellect of the mother, logic, etc.- are the letters of thought, just like in a person, in whom the letters of thought are an expression of their intellect (and emotions).
In Hashem’s four letter name, Havaya, ה -ו -ה-י, the letter ה' appears twice: The first ה' (after the י') corresponds to Bina and is called the “Greater Letter ה',” and the second ה', after the ו', corresponds to Malchus and is called the “Smaller Letter ה' .”
In Likutei Torah, in the maamar entitled את שבתותי תשמרו (Parshas Behar) the Alter Rebbe explains that there are twice as many letters of thought in the Torah as there are written letter in the physical Torah scroll. The reason brought is that in thought, the words appear with both consonants and vowels, and some of the vowels take up the space of letters, equivalent to 300,000 letters. (In the English language there are letters which are consonants and there are other letters which are vowels. But in Hebrew all the letters are only consonants, and the vowels are separate (called נקודות, of which there are 10 and are listed in the beginning of the Siddur separate from the Aleph-Beis chart). In the physical Torah scroll there no vowels – נקודות – written. However, in thought, words appear together with the נקודות, and, of those נקודות, some take the place of letters, equal to the 300,000 missing letters).
