Ending a sentence with period indicates that the speaker feels that there is no further need for discussion and has said all there is to say on a subject.
Some Excerpts:
From TV shows, movies and novels
Desperate Housewives
Nicollette Sheridan (Edie Britt) used the word “period” at the end of the sentence while talking to Teri Hatcher (Susan Mayer) in the popular TV [...]
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Slippery slope refers to a bad situation or habit which, after it has started, is likely to get very much worse.
Some Excerpts:
From TV shows, movies and novels
Sex and the City
Sarah Jessica Parker(Carrie Bradshaw), when out with her friends Kim Cattrall(Samantha Jones), Kristin Davis(Charlotte York), Cynthia Nixon(Miranda Hobbes) had used the phrase “Slippery slope” in Season [...]