It is another part of name that comes after the word root. There are two types of suffixes:

  1. Primary Suffix
  2. Secondary Suffix

Primary Suffix:

It is used to indicate whether the parent chain is saturated or unsaturated.primary-suffix

Note: If primary suffix begins with consonant like di, tri, tetra, etc. then extra “a” should be added to word root.
For Instance:
Number of C-atoms = 4
Word root = but
Primary suffix = 1-ene (Here, 1 is the position of double bond)
IUPAC name = word root + primary suffix
= but + 1-ene
= but-1-ene
= 1-butene (Also correct)

Secondary Suffix

It is used to indicate characteristics of functional group which is added to primary suffix.