In numismatics there are two major types of rarity, absolute and condition:
An example of absolute rarity is a 1913 Liberty Nickel of which there is only five known examples each essentially priceless. Because the Liberty Nickel is so scarce in any and all circumstances it has absolute rarity.
Conversely an 1886-O Morgan Silver Dollar in uncirculated condition is conditionally rare due to the lack of overall quality for the date. Despite relatively high mintage, just over 10 million, an 1886-O Morgan in uncirculated gem quality is nearly unobtainable with just 14 graded MS61 or higher by NGC.
Often collectors assume a relatively high mintage indicates the rarity of a particular date will be diminished, even though this is not always the case. For instance nearly half a billion Franklin Half Dollars were minted but less than 300 have been graded in MS67 or higher by NGC. In perspective for the entire series it’s less than one in 1½ million or .000067%, graded MS66 or better by NGC.