J

In physics, the symbol for joule, the SI unit of energy.

J

Tenth letter of the English alphabet. The English value of j is that of a voiced palatoalveolar affricate, as in ‘judge’.

It was one of the few permanent additions made in the Middle Ages to the Semitic, Greek, and Latin alphabets. In Latin, the letter i had the consonantal sound of today's English y, as well as being a vowel. In the early Middle Ages the symbols i and j were used for both consonant and vowel sounds. From the 14th century, the symbol j was used distinctly, particularly when written as the first letter of a word, or in conjunction with another i. The current English sound came via French, where it had become a voiced palatoalveolar fricative (as in the middle consonant in the English word ‘pleasure’), and thence to the English voiced palatoalveolar affricate. In French the voiced palatoalveolar fricative was also represented by g. Consequently some words in English, such as ‘gaol’, ‘jail’, have an alternative spelling of g and j. The Latin sound of j is still found in words such as ‘hallelujah’.