G often says /j/ when e, i or y come next — like in gem, giant and gym. But not always: get, give and girl keep the /g/ sound.
The rule
G commonly represents /dʒ/ before e, i or y. Unlike soft c, this has a substantial set of common exceptions, and several of them are among the first words a child reads.
What is really going on
The same Late Latin palatalisation that produced soft c, but applied to a mixed vocabulary. Words inherited from Old English and Old Norse kept hard g before front vowels — get, give, girl, gift, geese, gear, begin, forget — while words borrowed from French and Latin softened. The spelling does not distinguish the two sources, so the exceptions cannot be predicted from the letters.
Why English does this
Get, give, girl and gift are Germanic, and Germanic g did not soften. Gem, giant and gentle are French. The rule works on the French half of English vocabulary and fails on the Germanic half, and both halves are spelled the same way.
Position in the word
Beginning of a word — Soft in French-derived words, hard in Germanic ones. Not predictable. For example: gem, giant, gentle, get, give, girl.
Middle of a word — Usually soft. For example: magic, danger, engine, digit.
End of a word — As -ge or -dge, reliably soft. For example: large, cage, page, bridge, judge.
When this rule works
The letter after g is e, i or y.
Most reliably when the g ends the word as -ge or -dge.
When this rule does not work
The word is one of the Germanic set: get, give, girl, gift, geese, gear, gecko, begin, forget, tiger, target, giggle.
The g is doubled — a doubled g is hard: giggle, bigger, dagger.
The g is followed by u to force it hard: guess, guide, guitar.
Hard g before e, i or y: get, give, girl, gift, geese, gear, begin, forget, target, tiger, giggle, gild, gimmick. Germanic and Norse words, which never underwent the softening.
gu to force hard g: guess, guest, guide, guitar, guard, vague. The u is a spelling device, not a vowel.
Contrast pairs
gem versus get — The same letters, both common, different sounds — the pair that proves this is not a law.
giant versus give
gym versus girl
cage versus bag — The e is what makes the g soft.
Common reading mistakes
get: a child reads /dʒet/, where the word is /get/. Soft g over-applied to a Germanic word.
giant: a child reads /gaɪənt/, where the word is /dʒaɪənt/. Hard g applied where the word is soft.
Do not teach it like this
"G says /j/ before e, i and y, just like c says /s/."
The parallel is tempting and it is false. Soft c is near-exceptionless; soft g fails on get, give, girl and gift — four of the most frequent words in a child's reading. A child told the rules are the same will mis-read all four and conclude they cannot read.
"G often says /j/ before e, i or y — but not always. Try /j/, and if that is not a word you know, try /g/." Teach the flexing, and name the Germanic set explicitly.
Teacher note
Teach soft c first and let it be secure, then teach soft g as the one that is 'almost the same but less trustworthy'. Name get, give, girl and gift as a list on day one — a child who meets them as a known exception set reads them correctly; a child who meets them as surprises stops believing the rule. This is the single most important place in the phonics sequence to be honest about reliability.
Teaching sequence
Confirm soft c is secure first.
Introduce soft g at the end of words, where it is most reliable: page, cage, large, bridge.
Then at the start: gem, giant, gentle.
Immediately name the exception set: get, give, girl, gift.
Practise flexing: try /j/, then /g/, and ask which makes a real word.