Expression Number
The expression number is, in numerology, the number obtained by adding the numerical values of all the letters of the full birth name (first and last name), then reducing the sum to a digit between 1 and 9 or to a master number.
Origin and etymology
The calculation of the expression number belongs to the modern Western numerological tradition codified at the beginning of the 20th century by Mrs. L. Dow Balliett and then Juno Jordan. The letter-to-number correspondence table used (A=1, B=2, ... I=9, J=1, K=2, etc.) rests on the principle of theosophical reduction popularized by Madame Blavatsky at the end of the 19th century. This so-called Pythagorean table owes little to Pythagoras himself (6th century BCE): it derives more directly from Christian and Hebrew Kabbalah, where each letter carries a value. An alternative table, called Chaldean, uses different correspondences.
Evolution and tradition
The expression number is calculated on the full name registered at birth, including middle names. This precision matters: name changes (marriage, pseudonym) do not affect the natal expression number, but can give what is called a used expression number. The tradition distinguishes three sub-numbers: the soul number (sum of the vowels), the personality number (sum of the consonants), and the total expression number. This triad was stabilized by Florence Campbell in Your Days Are Numbered (1931). Chaldean numerology, rarer, rests on a table of only eight digits.
Practical use
The expression number is interpreted as the indicator of the potential to be expressed in this life: talents, modes of action, natural terrain. It is generally read alongside the life path. A person with life path 7 (inquiry) and expression number 3 (creativity) orients differently from a person with path 7 and number 8 (authority). On Tarotoui, the expression number calculation is available from the birth name, with an interpretation entry. The calculation can also be applied to a used name to study the image projected socially.
Going further
The choice of table (Pythagorean or Chaldean) gives different results, so you must specify the method used. The transliteration of foreign names or names with diacritics raises issues: some numerologists ignore accents, others transliterate them. Note also that numerology has no scientific validity. Confusing expression number with actual personality is a simplification.