• stop consonant + σ:
  • velar + σ > ξ;
  • labial + σ > ψ;
  • dental + σ:
    1. simple > σ;
    2. preceded by ν > compensatory lengthening + σ;

Examples:

• STOPS AND WORD ENDINGS - Greek words never end with a stop consonant. Apart from vowels, Greek words can end only with the consonants ν, ρ and σ, and of course with the double consonants ξ and ψ, since their final sound is actually σ. The words ἐκ οὐκ οὐχ are only seemingly exceptions, for they are proclitics and consequently they are perceived as integral parts of the following words. Therefore, stop consonants at the end of words are dropped at the word formation stage. Ed. *σῶματ > σῶμα, *ἐφεροντ > ἔφερον.
  

  ---

In order to explain the formation of certain Greek words, linguists have reconstructed a sound called jod in the Greek prior to the first literary records; this sound consisted of a semivowel quite similar to the i in the Latin word iam. The Greek alphabet has no corresponding letter, since the sound jod had disappeared from use before the alphabed spread in Greece. In the study of phonetics, however, in order to provide grounds for the explaination of certain phenomena, it will be inevitably necessary to refer to this sound, conventionally represented with the symbol j. The combinations of stop consonants and jod originate different outcomes, which are dealt with on the page covering consonantal changes connected with jod and digamma.

A phenomenon called dissimilation of aspirates sometimes occurs in word inflection. It is important to be aware of such behaviour in order to correctly look up words in dictionaries. For a better insight, go to the page related to the dissimilation of aspirates, also known as Grassmann's law.