Peptid

Peptid is a term that appears in a small subset of biochemical literature. In modern usage, the standard term for a short chain of amino acids linked by peptide bonds is "peptide"; "peptid" is largely obsolete or regional and is rarely used in contemporary journals. When encountered, peptid is typically used as a synonym for peptide or to designate a peptide fragment generated by hydrolysis of a protein.

The form likely derives from the same root as "peptide," from Greek peptikos meaning "digested" or "able to be digested." In chemistry and biochemistry, the -id suffix has been used in older or non-English sources to denote a derived or fragmentary unit, which may explain historical occurrences of "peptid."

In current practice, there is no formal, universally accepted definition of "peptid" in contrast to the well-defined terms peptide, oligopeptide (short peptides), and polypeptide (long chains). Therefore, if encountered, the term should be treated as archaic or context-specific. Most reliable sources will prefer "peptide" to avoid ambiguity, while "peptid" may appear in historical texts or in multilingual contexts where direct translation is used.

Overall, "peptid" is not a widely recognized or standardized term in modern biochemistry. For clarity, use "peptide" for short amino acid chains, and reserve "oligopeptide" or "polypeptide" for more precise length-based distinctions.