Could someone please provide two simple sentences that clarify the difference between these two phrases.

Thanks!

Bhí daoine go leor ansin / Plenty of people were there (lots of people)
Bhí na daoine go léir ansin / All the people were there (everybody was there)

Am go leor / Plenty of time
An t-am go léir / All the time

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Táim ag foghlaim fós. Fáilte roimh gach aon cheartúchán.

Thanks!

Yeah, go léir means all ; go leor means enough or many.

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Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

re go leor, I would use go leor before a noun and after an adjective.

Ní raibh go leor ama agam - I didn't have enough time.

Tá sé fuar go leor inniu - It's quite cold today.

Certainly after an adjective, but either before or after a noun. (Learning Irish has seomraí go leor and go leor seomraí and equally as many examples with go leor before as after.)

Also go leor is found before verbal adjectives (because it is then functioning as a noun) - tá go leor déanta acub, tá go leor ite 'am, etc.

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Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).

If it's in Learning Irish, well so be it. It could be used widely, but I must say I've never heard it and I can't find an example in FBG.

Ah, Scoob, you won't find any there. You have to look in FGB.

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I am only a beginner. Please get confirmation before using any of my suggestions.

"Bhí daoine go leor ansin" níl aon chiall le sin.

Ciallaíonn sé "There were lots of people there" i gConamara, creidim.

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Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).