Arabic dictionary
Dictionary Arabic-English Lexicon by Edward William Lane (d. 1876)
Entry لكن
لُكْنَةٌ An impotence, or impediment, or a difficulty, in speech or utterance; (Msb;) a barbarousness, or viciousness, and an impotence, or impediment, in speech: (S:) or the not speaking Arabic rightly, by reason of a barbarousness, or viciousness, in the tongue: (K:) or the interposing of [words of] a foreign language in one's speech. (Mbr, TA.) See تَهْتَهَةٌ; and عُجْمَةٌ, with which it is syn. لٰكِنْ, with the ن quiescent, has no government.
It means But after a negative proposition: but not after an affirmative: see إِلَّا.
E.W. Lane's Arabic-English Lexicon (8 parts, London, 1863-93) is a major Arabic-English dictionary based on 112 sources, mostly medieval ones, along with al-Zabidi's Taj al-Aroos (also included in Lisaan.net). Lane died before he could finish the work, his great-nephew Stanley Lane-Poole finished it, publishing Volumes VI, VII and VIII from 1877–1893 using Lane's incomplete notes. Lane-Pool's work is of lower quality than Lane's. The work of Reinhart Dozy (see below) was meant as a supplement to Lane's work that covers modern Arabic (Lane focused on classical Arabic only). The digital text for the Lexicon was sourced from Tufts University under a Creative Commons Attribution-ShareAlike 3.0 United States License. We used a TXT version created by an internet user named Navid-ul-Islam. Lisaan.net's version of the Lane Lexicon corrects various errors from both the Persues project (such as erroneous transcriptions of the Persian letter ژ) and the TXT version. Lisaan.net's version also provides helpful automatic annotations on the various abbreviations used by Lane.