Why are "just" and "justice" written with a "j", while "language" is written with a "g", when they all come from Latin?

Question

The word "language" comes from Latin and is written with a "g". The adjective "just" and its noun form "justice" also come from Latin. These are the only words Latin origin I am aware of that are spelled with "j", even though "j" did not exist in Latin. Given that all these words are from Latin, why could English not spell "just" and "justice" as "gust" and "gustice" when "language" is still written as "language" only and neither as "lanjuaje" nor as "languaje"? How did the Latin words get adopted into English differently?

Answer 1

The consonant "g" has rules (which have many, many exceptions) about when you pronounce it /g/ and when you pronounce it /dʒ/.

When it's before a "u", "o", or "a", like in the words gut, got, and gape, "g" is almost always pronounced /g/.

When it's before an "e" or "i", it can be pronounced either /g/ or /dʒ/. Generally, it's pronounced /g/ in words of Old English or Germanic origin, like get and gift, and /dʒ/ in words of French or Romance origin, like gel and giant. This reflects the spelling of these words in their original languages. However, because English spelling is so mixed up, there are lots of exceptions to this rule, like gibberish, ginger, and tiger.

So because just and justice are pronounced with /dʒʌ/, where the vowel is represented by "u", we need to spell them with a "j".

Answer 2

The adjective "just" and its noun form "justice" also come from Latin. These are the only words Latin origin I am aware of that are spelled with "j", even though "j" did not exist in Latin.

There are many more words of Latin origin that are spelled with "J": it's a normal spelling pattern for words where the Latin letter I represented a non-syllabic consonant sound rather than a syllabic vowel sound.

"J did not exist in Latin" is true in the sense that J was not a distinct letter from I. In the exact same way, J also did not exist in English as a distinct letter from I until sometime around the middle of the second millenium AD.

The first OED citations for just show this:

c1384 Bible (Wycliffite, E.V.) (Douce 369(2)) (1850) Deeds vii. 52 The prophetis..that bifore teelden of the comynge of the iust [1611 King James the Iust one; L. Iusti].
?1483 W. Caxton in tr. Caton iv. sig. hij It is seen selde, the Iuste to dekaye ne to haue nede in suche manere, but that he hath euer good ynough for to fede and susteyne hys lyf naturalle.
1526 Bible (Tyndale) Acts vii. 52 That iust whom ye haue betrayed.
1535 Bible (Coverdale) Psalms xxxvi[i]. 12 The vngodly layeth wayte for the iust, & gnasȝsheth vpon him with his tethe [so 1611 and R.V.].
1664 Bp. J. Taylor Disswasive from Popery ix. 210 Christ is not our Advocate alone, but a Iudge: and since the just is scarce secure, how shall a sinner go to him, as to an Advocate?

You can also see in these quotations that V was used for a vowel sound at the start of a word, and U for a consonant sound in the middle of a word.

In Classical Latin, consonantal I was pronounced as [j], but this pronunciation evolved in some languages to [dʒ] at a time much earlier than the introduction of J as a distinct letter; in fact, the value [dʒ] for consonantal I most likely developed before these words entered English, as it was probably used in older forms of French (present-day French has [ʒ]) and taken into English from that source. (Alternatively, English speakers may have sometimes adapted French [ʒ] as [dʒ].) After this evolution, consonantal I had the same sound as the letter G, but only in certain contexts: G was a regular spelling of the sound [dʒ] before E, I or Y, but not before other letters such as U, as Peter Shor's answer explains.

At the time the words just and justice were taken into English, then, they had the sound [dʒ], but were spelled with the consonant letter I just as in Latin: the spelling of the consonant wasn't changed at all when its sound changed or when the words were borrowed. It has never been regular in English to respell I/J as G or to respell G as I/J in words from Latin or French, although it has at times occurred, mostly in words where the sound is [dʒ] and the letter comes before E, I or Y. The first G in language does not make the sound [dʒ]: the second G does, but essentially no English words end in the letters "aje", so it would not be perceived as a reasonable alternative to the spelling "-age".

When the letter I came to be reserved for vowel sounds, the letter J replaced consonantal I wherever it occurred: not only in words of Latin origin containing the sound [dʒ], such as just and justice, but also in words with other origins such as jar (formerly spelled iarre; taken from French and ultimately from Arabic), jaw (uncertain origin; formerly spelled iow(e) and iawe), joy (from French; former spellings ioie, ioy, ioye, goye), jest (from French; former spellings gest(e), iest(e), ieast).