Even though the concept of linguistic variant has been fully established in contemporary sociolinguistic studies, it demands a theoretical review when it is considered from the perspective of lexicon studies, especially when related to historical and variational biases. In this paper, we present limits on identification and characterization of lexical variation, considering formal changes that may occur at other levels of analysis, especially at the morphological or phonetic ones. To support the reflections on the topic, we discuss the process of lexicon constitution in Portuguese and the results of etymological convergence and divergence present in the history of the language. Based on the analysis presented, it is proposed that research on lexical variation should incorporate to this notion any significant formal or content changes.