The primary aim of this article is to provide an overview of perfluoroalkyl and polyfluoroalkyl substances (PFASs) detected
in the environment, wildlife, and humans, and recommend clear, specific, and descriptive terminology, names, and acronyms
for PFASs. The overarching objective is to unify and harmonize communication on PFASs by offering terminology for use by the
global scientific, regulatory, and industrial communities. A particular emphasis is placed on long-chain perfluoroalkyl acids,
substances related to the long-chain perfluoroalkyl acids, and substances intended as alternatives to the use of the long-chain
perfluoroalkyl acids or their precursors. First, we define PFASs, classify them into various families, and recommend a pragmatic
set of common names and acronyms for both the families and their individual members. Terminology related to fluorinated polymers
is an important aspect of our classification. Second, we provide a brief description of the 2 main production processes, electrochemical
fluorination and telomerization, used for introducing perfluoroalkyl moieties into organic compounds, and we specify the types
of byproducts (isomers and homologues) likely to arise in these processes. Third, we show how the principal families of PFASs
are interrelated as industrial, environmental, or metabolic precursors or transformation products of one another. We pay particular
attention to those PFASs that have the potential to be converted, by abiotic or biotic environmental processes or by human
metabolism, into long-chain perfluoroalkyl carboxylic or sulfonic acids, which are currently the focus of regulatory action.
The Supplemental Data lists 42 families and subfamilies of PFASs and 268 selected individual compounds, providing recommended
names and acronyms, and structural formulas, as well as Chemical Abstracts Service registry numbers.