[masaegu]

Thanks, everyone, for your reply!

As KyleGoetz stated, this phenomenon is named 「ら抜（ぬ）きことば」, literally meaning "ら-omitting words" and it is a major trend in our language. It occurs in the potential form of certain verbs. It has already existed for decades in the speaking part of the language, particularly among children.

The striking difference during the last decade or so is that many adult speakers have been using the 「ら抜きことば」 not only in casual speech but also in fairly formal and/or business situations. Even now, you would surely be corrceted if you used it in writing both in school and business. In people's day-to-day conversations, however, it appears utterly unstoppable.

Though I have been hearing it all my life, it still shocks me to visually see the 「ら抜きことば」 in advertisements such as the images above show. In any kind of formal writing, you will NOT see it. But how do we explain this to children or those who are studying Japanese as a foreign language? "In wide use but incorrect"? "Correct only by popular vote"? I happen to have grown up in a home that was and still is completely free of 「ら抜きことば」 and recently I feel like the foreigner in my own country.