What is a "Ru'ach Kin'ah"?
Rashi: It is a spirit of jealousy that prompts him to take action.
What does "Vekinei es Ishto" mean?
Rashi: It means that he warned his wife not to seclude herself with the man whom he suspects of having an affair with her. 1
A precondition to becoming a Sotah.
And what are the implications of "Vekinei es Ishto ve'Hi Nitma'ah ... ve'Kinei es Ishto ve'Hi Lo Nitma'ah"?
Rashi and Rashbam: It implies that he warned his wife not to seclude herself with the man, and she did, but he does not know whether they were intimate or not.
Seforno: It means that he warned her either because he was imbued with a spirit of jealousy, when he realized that she had departed from the path of Tz'niyus, or for no apparent reason, and either way, she contravened his warning.