As @Danielillo pointed out in his comment, there is not a single rule that can be used to determine whether a soft "G" or a "J" should be used. However, there are some guidelines that can be useful for some scenarios.
Here is the link to the site where I extracted this information from: SOFT G / J. My answer is a summary of the points I thought were most important for a Spanish learner. The site goes into some more detail and gives a couple of more "rules". Hope this helps!
When to use "G"
1. Verbs ending in "-ger" or "-gir" are generally written with a "G"; here are the most common exceptions: "tejer" (to sow), "grujir" (to grunt) and "crujir" (to creak or to crunch) and their derivatives, like "entretejer" (to interweave).
2. Words beginning with "gene-", "geni-" or "genu-"
3. Word ending in "-gen"; apparently there is only one exception to this rule, but as a native speaker I did not even know what that word meant
When to use "J"
4. Verbs ending in "-jear"; once again, there seems to only be one exception, but I think you probably won't encounter it.
5. All nouns ending in "-jero"
6. Words beginning with "eje-"; there are very few exceptions and the same comment as in point 4 applies here
ONE LAST COMMENT
If a verb does not contain the soft g / j sound in its infinitive form, but when conjugating the verb the soft g / j sound appears (in whichever tense the verb is being conjugated in), then a "J" will be used. Some examples:
"decir" (to say) - no soft g / j sound in the infinitve
Past simple: yo dije, tu dijiste, usted / el dijo, nosotros dijimos, vosotros dijesteis, ustedes / ellos dijeron
Another example is the verb "traer" (to bring) and verbs ending in "-ducir", like "traducir" (to translate)
If a verb contains the soft g in its infinitive form, like "proteger" (to protect), and a soft g / j sound appears in a conjugated form of the verb, a "G" will be employed.
Answer from Agustin G. on Stack ExchangeI’m brand new to Spanish (only learned the alphabet so far) and I’m not able to tell the difference in both speaking these two letters (I’ve been pronouncing them the same way essentially), and differentiating them when listening. Both letters have just been explained to me as it sounds kind of like you’re clearing your throat.
Videos
!hola! good people of r/spanish. I would appreciate it very much if anybody could give me some insights on the pronunciation of "G" and "J". I know the theory from many learn Spanish websites, but still appreciate a few tips from native speakers/learners already fluent in Spanish. Firstly, "g", I know it sounds is "khe"....well until I read yahoo en espanol where Prince William is referred to as "el principe Guillermo" and Princes Diana as "Diana de Gales". How do you pronunce Guillermo and Gales in Spanish? Also, Guadix, how do you pronunce it? is it "wa-dih", and if so why it is not spelled like Oaxaca (wahaca)? Secondly, what is the most acceptable sound of "j"? is it english "h" sounding or english "y" sounding? Is jesus pronunced as "he-sus" or "yee-zus"? and a few days back I saw this headlines in one of Spains TV channels "antiyihadistas operacion en madrid". so how do you pronounce it "an-ti-YEE-ha-dis" or like the English "an-ti-JEE-ha-dist".Thank you very much from me personally to each and every reply.Gracias.
~I’m very new to learning Spanish~ So the j has an “h” sound and the g is mostly the “g” sound in English too. But I noticed g sometimes makes an “h” sound like in inteligente. Is that the only word that uses g like that?
When the words are foreign words and adopt the original phonetics.
Banjo comes from English, in Spanish there are both Banjo and Banyo, as it is pronounced.
Ninja comes from the Japanese and is pronounced with its original phonetics.
I didn't find any another word with "nj" from 2900 pronounced as the English "j".
But, sometimes the "j" is pronounced as in English in some words, especially anglicisms. For example:
- Jean is never pronounced j.e.a.n but as "dʒin" (Spanish pronuntiation)
- The same with Jogging, Jet, Jet set, Jet lag, Jumbo, Jazz, Junior, words all accepted in the RAE.
Sometimes it depends on the meaning or use:
Jaguar the animal is pronounced like the Spanish "j"
Jaguar the car, like the "j" in English
Ginebra is pronounced with the Spanish "g", similar to the Spanish "j" sound
Gin is pronounced with the original English phonetics
The same happens with some Gallicisms, where the j or g are not (or rarely are) pronounced with the Spanish sound but with the French one:
- Beige, Collage, Déjà vu,
- Garaje, with the original phonetics in Latin America, not in Spain.
And of course all personal names: John Travolta, Michael Jackson, Norma Jean, Jean Luc Godard, Jessica Rabbit.
@Danielillo's answer is mostly correct, but the sound isn't exactly like English ⟨j⟩ [d͡ʒ]. Rather, it's somewhere in between English ⟨j⟩ and English ⟨y⟩, a sound which doesn't exist in English — [ʝ] or [ɟ͡ʝ]. This sound is the same as the ⟨y⟩ in “yo” or the ⟨ll⟩ in “llamar”.
However, note that there's a wide variation in how this sound is pronounced in different regions, speakers, and contexts — [ʝ], [ɟ͡ʝ], [ʒ], even [ʃ]. And in some places, the pronunciation of ⟨ll⟩ is different from that of ⟨y⟩ (see yeísmo).
So, the more accurate answer to "When would Spanish speakers pronounce ⟨j⟩ like English ⟨j⟩ [d͡ʒ]?" is "never". But they pronounce it similarly ([ʝ~ɟ͡ʝ]) in loanwords from other languages, such as "banjo" and "ninja".