In many North American dialects, there are ten or eleven stressed monophthongs; only five or six vowel (rarely seven) contrasts are possible before a preconsonantal and word-final ("beer, bear, burr, bar, bore, bor, boor"). Often, more contrasts exist if appears between vowels is not in the same syllable. In some American dialects and in most native English dialects outside North America, for example, "mirror" and "nearer" do not rhyme, and some or all of "marry", "merry", and "Mary" are pronounced distinctly. (In North America, those distinctions are most likely to occur in New York City, Philadelphia, some of Eastern New England (including Boston), and in conservative Southern accents.) In many dialects, however, the number of contrasts in that position tends to be reduced, and the tendency seems to be towards further reduction. The difference in how the reductions have been manifested represents one of the greatest sources of cross-dialect variation.