Language has always changed, but the Internet has noticeably increased the speed of language change, not always for the better.
It's extremely easy to adopt new terminology unthinkingly because everyone else is using it without realizing the social effects. Language both reflects and influences culture. It's one of those round and round, chicken and egg cycles that can never be precisely pinned down. Lex orandi, lex credendi always has its parallel in the world of ordinary speech.
To move from the general to the specific, I present five more or less neologistic usages, usages that have changed or come into being in the last twenty years at most (by my guess). All five tend to downplay the importance of marriage and the distinction between marriage and non-married states:
1) The use of "partner" to mean "whomever you happen to be having sex with regularly, whether male or female, married to you or not." Not so very long ago, "partner" meant someone with whom you are carrying out a business venture or some other undertaking, such as exploring the North Pole. In the late 80's and early 90's, by my estimate, it started to be a code word for "homosexual lover," because homosexual "marriage" wasn't up and running yet, and "friend" didn't convey what a man wanted to say when referring to this particular category. From there, it morphed into an all-purpose term for "fairly regular sexual partner," presumably because of a vague desire not to use it exclusively and hence in a "discriminatory" fashion to refer to homosexual couples. Now it seems to be used in the way given above.
This usage undermines marriage by implying an equivalence not only between homosexual and heterosexual unions but, even more often, implying that the distinction between married and unmarried heterosexual couples is unimportant. Don't use "partner" this way. Use more precise terminology: "Husband," "wife," "live-in boyfriend," and so forth.
2) The use of "ex" to mean "former boyfriend" or "former girlfriend" rather than a person to whom one used to be married. I think we can be pretty sure that in the country song "All My Exes Live in Texas" the women in question are supposed to be ex-wives. That's what gives the song its slightly bawdy humor. I still find it extremely confusing for a person to use "ex" to mean "ex-boyfriend." It never meant that thirty years ago, and it always makes me do a double-take and wonder if the speaker is actually divorced.
This use of "ex" creates the impression that breaking up with a person you aren't married to is just as serious, or just as un-serious, as getting a divorce. It also downplays the importance of actually identifying oneself as divorced by making it more difficult to distinguish a locution in which a person is implying that he is divorced from a statement that merely implies that he once had a girlfriend who is no longer his girlfriend. Again, it's much better to be clear and precise. Use "ex-girlfriend" or "former girlfriend," or "ex-boyfriend" or "former boyfriend," or even "ex-fiance," whichever applies, not simply "ex."
3) Related to that use of "ex" is the use of "single" for oneself if one is divorced. Yes, we all want our privacy, but actually, it often is someone else's business to know if you are divorced.
I'm sorry, but if you are divorced, you are not unambiguously single. For one thing, some people have metaphysical beliefs about that--e.g., whether divorce is even metaphysically possible. And you never know, they may be true. For another thing, a person who is divorced has, perhaps through no fault of his own, various types of "baggage" that a never-married person doesn't have. To put it bluntly, it isn't fair to someone who might fall in love with you or think of you as a marriage prospect to refer to yourself as "single" when you are divorced, because it might make a difference to that person, and it shouldn't come out as a surprise later on.
This use of "single," like some other usages in this list, implies that the distinction between being divorced and not being divorced is unimportant. That implication, in turn, undermines the importance of marriage. Whatever one's theological or social theories about divorce, we ought to be able to agree that it isn't unimportant. Our language, once again, should be clearer.
4) The use of "relationship" to refer to any sort of serious or semi-serious romantic connection, usually involving sex, whether involving marriage or not. See above on "partner." All "relationships" are not created equal.
5) Here's another misuse of "single"--the use of "single" to mean "not dating anyone" rather than "not married." A young woman, never before married, who has a serious boyfriend is nonetheless single. She may be on the way to becoming non-single, but she is single right now. To imply that everyone who is "in a relationship" or who "has a partner" is not single is ipso facto to downplay the importance of marriage and the distinction between being married and being unmarried.
I first noticed this use of "single" while reading a most unfortunate column by a young woman who was setting herself up to give dating and...other...advice to other young women. The advice came from a decidedly secular perspective. In the column in question she was implying that single people are not having sex, using "single" merely to mean "not in a relationship." What's the implication? That anyone who is dating someone even semi-seriously is having sex and that the only people, poor fools, who are stuck with celibacy are those who can't find anyone to be a sexual partner. Marriage? What in the world is that? This use of "single" causes marriage to drop out of the picture altogether.
What is happening in our world is not that unmarried sexual relationships are becoming more and more serious. Instead, all sexual relationships are being boiled down into an undifferentiated stew of uncertainty, unclarity, and ephemerality. Marriage is decidedly the loser in this process.
So if you realize the importance of marriage and have found yourself unthinkingly using any of these words in these ways, this could be a useful wakeup call to think again and recalibrate.