Why do linguists use an asterisk before reconstructed Proto-Afro-Asiatic words?

In linguistics, an asterisk () is used to indicate that a word or sound is a reconstruction* rather than an attested, documented form.12

When linguists study language families like Afro-Asiatic, they use the comparative method to analyze phonologies, vocabularies, and grammars across related languages. Because these ancestral forms—such as Proto-Afro-Asiatic—are hypothetical common ancestors that were never recorded in writing, they are marked with an asterisk to signify their status as theoretical constructs.13

These starred forms serve as essential tools for researchers to summarize the systematic correspondences observed between daughter languages. While some linguists view these reconstructions as purely abstract formulas, others attempt to assign them phonetic interpretations to better understand the historical development and nature of the relationships between languages.13