لكن أن: but to (..) لكن أنا: but I (..) لكنني is indeed Fusha.

there are two different articles: لَكِنْ (read laaken) لَكِنَّ (read laakinna with shadda on the noon) both of them mean but/however but they have a slightly different usage -------------------------------------------------------- لَكِنْ laaken (the first one) is simple it's just a conjunction that connects two sentences or words. for example: بَحَثتُ عَن مِحفَظَتي وَ لكِنْ لَم أَجِدهَا I looked for my walled *but* I couldn't find it لَكِنْ can also be followed by أَنَا for example: تَعِبتُ كَثِيراً لَكِنْ أَنَا سَعِيدٌ I got very tired, *but* I am happy Laaken can also be used to connect two words for example: لَم أَشرَب اللَبَن لكِن المَاءَ فَقَط I didn't drink milk *but* water only --------------------------------------------------------- لَكِنَّ (with shadda on the noon) is different. it's one of the sisters of إنَّ (Inna) After laakinna there should be a complete sentence for example: لَدَينَا مَاءٌ لَكِنَّ الطَعَامَ قَلِيلٌ We have water but the food is very little لَكِنَّ can't be used to connect two words Another difference is that when laakinna is followed by a pronoun it must come in the attached form so you can't say : لَكِنَّ أَنَا سَعِيد this is wrong. It has to be : لكنَّنِي سَعِيد but I am happy Similarly you can't say: لَكِنَّ هُوَ سَعِيد it should be لكنَّهُ سَعِيد I hope this clarifies the differences between the two :)