Percent is from the Latin adverbial phrase per centum meaning “by the hundred.” The Latin phrase entered English in the 16th century. Later, it was abbreviated per cent. with a final period. Eventually, the period was dropped and the two parts merged to produce the modern one-word form percent. The two-word form per cent is still used occasionally, but its use is diminishing. The percent sign (%) is used chiefly in scientific, tabular, or statistical material and only with numerals preceding it: 58%; a range of 30% to 40%.
In the senses “rate or proportion per hundred” and “proportion in general” percent and percentage are frequently interchangeable. With a preceding number, only percent occurs (a 16 percent decline); with no preceding number, either occurs, but percentage is much more common: a certain percentage (or percent) of the land.