Term for the day: "Semantic bleaching"

In a column at the New York Times this week Ben Zimmer ruminates about the use and misuse of the word "anniversary":

What has happened to the word anniversary? Even though the idea of yearly recurrence is built into the word etymologically, that idea has been clouded over centuries of use...

As the annual aspect has moved to the background of anniversary, the shift has opened the door for use of the term to mark the passing of shorter units of time. The 11th edition of Merriam-Webster's Collegiate Dictionary, in its entry for the word, states that anniversary can refer more broadly to a date following a notable event "by a specified period of time measured in units other than years," giving the example, "the 6-month anniversary of the accident."

Linguists call this process "semantic bleaching": the lessening of a word's force through generalization. The bleaching of anniversary has been going on for quite a while, even if dictionaries are only now catching up. For more than a century, English speakers have been modifying anniversary with numbers of days, weeks or months...

Anniversary has been pressed into service for nonannual commemorations in part because English has no other commonly used terms that can fill the gap. At various times since the 19th century, the monthly equivalent of anniversary has been dubbed a mensiversary...

More at the link.